Error with fibre-optic (Dynaudio) & bluetooth audio skipping

Lewis: The aspect of your error message that stands-out (for me) is "sporadic disruption". This means that the fault is intermittent which suggests (to me) that it's not a software problem - it's a hardware problem. The topology of the optical data bus for the digital sound system is like this:

So I took my unit out tonight to fit my new MIB2, in prep for upgrading it at some stage this week. 

Fakra connectors and fibre-optics look like this: 





You can see that, at least with the connectors themselves, they are in fantastic condition. There is a small split in the outer-casing for them but as I've been in here so rarely (first time was in early April, as-per OP) but I doubt that's the issue. 

I've OBDII'd the car twice tonight. I'll do it again tomorrow but there were no errors relating to this there - not with the old unit tonight and not with the new one. Because of CP, I can't test the audio output of the new unit to confirm lack of audio 'clipping' but that will be among the first things I do with it this week when the job is done. 

Given the intermittent nature of the audio issues themselves, I'm inclined to believe that the problem may actually be more to do with bluetooth interference from other vechicles than any kind of long-term damage to the fibre. No one has been in there and given the value I place on the stereo (you can take anything else about the car from me, PLEASE leave me with that) I was, and always have been, phenomenally careful when removing those connections from the back of the MIB. There is no way they can have been damaged, the splits in the plastic casing could have always been there from when the unit was first pushed into the slot, during manufacturing. 

I don't get any audio issues using any other audio source, not even the radio. Which leads me to believe there are just too many other people on the road using bluetooth to stream audio to their cars nowadays and we're crossing paths with each other. What's irritating is the fact that once the stream is contaminated - that's it. I have to reset the MIB using the power button if I want to resolve the issue, and I'm not even guaranteed that will do it when it comes online and re-establishes the connection to my phone... 

I hate to say it but sometimes wires really are all that and a bag of chips! 

It might help if I explain how I got here. I'm not saying that the unit is reporting bluetooth interference as a problem with the fibre-optic - there is every chance I am conflating two things here as I work through it and rule things out - it's that I can't get to the bottom of what's causing the audio to drop the way that it is. 

So, I've ALWAYS used the car with either an iPod, or an iPhone, connected with the appropriate cable via MDI. Historically, I haven't used bluetooth for audio streaming - except for on short runs - because of the battery drain and the lack of ability (although only with MIB1, as I learned after playing with my new unit this week) to browse the content of the phone from the unit, rather than using the phone.

On the odd occasion, I would notice the bluetooth audio skipping, but would't think anything of it as it was so infrequent.

As the software on my iPhone has matured however, the MDI has become harder and harder to use with it - to the point where I've just stopped using it altogether and now use bluetooth 80-90% of the time.

About 5-6 weeks ago, I was messing with the sound settings when I noticed the subwoofer option was missing from the menu. A quick scan revealed the error with the fibre-optic which prompted this thread. I think I rebooted the unit and it brought the sub back, I cleared the error and that was that. I was a little concerned however - at this stage, I didn't know a lot about the wiring for the stereo and I had recently found water in the spare wheel well (turned out to be the clogged tube from the rear emblem) - and I worried that something had in-fact gotten damaged with that.

It's only been since the end of March that I've began to notice real disruption to the audio stream when playing over bluetooth. I've been reduced to using it solely for the last 3-4 weeks, as I fitted my new USB module and wiring loom ahead of my MIB2 retrofit - rendering it useless until that was completed. What's interesting is that it's not always there (and neither is the error/fault reported with the fibre-optic) and the interference appears to be at it's worst along one particular stretch of road (which, by admission, I drive almost daily) although there are no radio beacons, pylons or lines there which would be giving off any radiation that could potentially knock it out. Even then, I'd expect to be able to pinpoint the location and ignore it - once the interference is there however, it's rhythmical and doesn't go away, so it's not even as if there is one particular car model, or mobile device, which could potentially be triggering it. 

If I use another source (a CD, or the radio) it doesn't happen. At all. Along the stretch of road where I knowingly get bluetooth interference, or any other - not even in the city centre. 

I have since learned that there was a S/W release for the Composition Media system which had a bug in it that caused the Sub to disappear from the Sound menu. My unit is out now but having learned this, it's likely that this was the issue. Not once, in nearly 8 years, have I seen this happen before. 

So, we're now at the stage where I'm still suffering with bluetooth interference (although phone calls appear to be fine) with this intermittent, almost phantom issue with the fibre-optic. Bearing in mind that the first time I saw this error with the fibre was before I removed the glovebox to dismantle the heater unit and extract the core for flushing, so anything which may have had the potential of being done to it since then (I've had the MIB out a handful of times since, testing various MIB2 units for suitability) are likely not the cause. 

I know others have reported the issue with bluetooth skipping and I'm beginning to think it's just the case that there are a lot of people doing this now and the space is becoming congested. If I do it on a totally clear stretch of road, I can enjoy the audio perfectly, so it certainly seem that way. Where my family are from, it's very popular for people to drive German cars and to opt for higher-end models/trims, so it's entirely likely that the number of VWs/Audis on the road around Aberdeen may well be a part of the issue. However, I have tried to take note of what's around me when I start to hear the clipping start and again, I'm struggling to find a common denominator. 

I am beginning to wonder if, given the error was there before anyone had handled the MIB unit to begin with (apart from when it was first installed) what's actually causing this issue is a software fault than anything else. My new MIB is in and CP has been removed - my tech ran out of time so I currently have no FECs installed (we're doing that tomorrow) but my plan is to test this thoroughly with the new unit, ignoring CarPlay for now, to see if the Fibre error continues to pop-up or if, in fact, after writing out all of this, it turns out to be nothing more than a red herring, in which case another bug in VW's software has been uncovered. 

I'm not sure if that bodes well for the intentions I read they have for taking more of their S/W development in-house... 

A little long-winded - you can blame my latent neurodiversitr for that - but does that give some kind of indication of my...call it a thought process...here? 

lth0ms0n just wondering if you're still dealing with this issue? i'm having pretty much the same problem as you and i believe it started when i replaced my stock MIB2 with a Harman MIB2.5 (High). I was getting the "sporadic disruption" error code, though not anymore for some reason, but every time i go for a drive and play music over Bluetooth, the music will stutter and/or cut out and then play faster than normal to catch up which sounds kind of funny. the MIB unit will also sometimes completely disconnect from my phone and i'll have to select the device again from the list.

the fault code points to a fiber issue but it really seems like a Bluetooth problem to me. i still need to try a different device like my laptop or something to see if maybe it's my phone (iphone 12 pro max). alternatively it's the head unit itself which would be sad if it has a Bluetooth issue. though maybe i should expect some weirdness because it's an Audi unit that i converted to Volkswagen and has component protection + FECs patched out.

i am also in the middle of a speaker + amp retrofit so if that solves the issue i'll post an update. i'm about to replace the Fender amp with a Focal and run the speaker wires from the MIB to the new amp under the driver seat, disable MOST, etc. i'm not too hopeful that this will solve the issue but who knows, maybe it will!