Interesting. I found exactly the same behavior. It starts like clockwork right around 50 minutes. I also experience garbled audio, and it gets worse if you play more than one source at the same time.
I spent a few months trying to get Apple support to fix the issue. They've done nothing. So in the last phone call I asked for Executive Customer Service. (They don't connect you via phone, you have to write a letter and send a fax.) Anyway, in the call I asked them how technical issues are ranked by support.
The Customer Relations agent explained how Apple's entire internal system for technical issues works. This is what he told me, (and what he strongly recommends is the only way to get this issue looked into ASAP.)
Apple addresses technical issues by rank. The ranking is determined by voting on issues. He told me this issue has TWO votes. (Yes, you read that right. two votes only.)
He also said that support has no means to escalate or vote on an issue. Support is forced to accept Engineering's instructions. Customer Relations also have no power to escalate or vote on issues.
(This next bit comes from an article I'll link at the bottom where an ex-Apple engineer explained the issue.) Ironically, Engineering cannot address issues unless they are assigned to them by Project Managers. So even if a software engineer wanted to fix the issue, Apple's corporate structure prevents them from being able to do
anything. All prioritization happens by the project managers that oversee the software engineers. Even worse, project managers can override decisions made by Software engineers.
Anyway... I asked him if what i see reported in these threads are true than how is it possible that the Apple Store has been replacing machines but the issue hasn't been considered a priority for voting...
He threw a few scenarios at me, and stated that he has no way to confirm if the scenarios are part of the issue... That said it does explain the why I keep seeing different threads where people report they're on their 2nd or 3rd machine with the same issue...
Scenario:
People are most likely returning the machines instead of phoning support to report and document the issue. Since the store has no way to address the issue, all they can do is replace it. Although the store is supposed to be thorough in what they document about the replacement, there's nothing that prevents the employee from just writing something like "sound is broken", or "speakers sound blown", etc... If the employee handling the replacement isn't familiar with the issue it's very likely they don't write much more than that..
He recommended I post the following in threads about the issue:
A. He does think the issue is most likely software-based.
B. If people are going to have their machine replaced, they should phone support first and report a detailed description of the issue with video documenting the behavior. Replacement can still be done after the fact..
C. Just bringing the machine into the Apple Store increases the likelihood that the person replacing the machine doesn't provide enough information to correlate the replacement with the issue.
D. Getting the issue resoved is unfortunately going to require en effort from people experiencing the issue. The short version is... Because of how Apple's voting system prevents anyone outside of project management to escalate an issue, the only way the issue's going to generate enough concern ASAP is by as many people logging the issue with support, sending as much documentation as possible before replacing it.
E. Submit video, and/or screen recordings of the behavior before replacing the machine.
F. He encouraged people to submit letters to Tim Cook's office. This is the only office that has the ability to prioritize an issue down the chain to Engineering.
G. If you decide to contact Tim Cook's office you'll want detailed documentation anyway. If you have no video and/or documentation proving the issue they have nothing to work with. (Also, realize Cook's office is constantly fielding issues users feel are priority... If they're going to explore the issue your case needs to be compelling...)
That's the unpleasant reality of the situation :(
We're basically stuck having to report to support. Support will most likely shoot the issue down. Ultimately the only thing that's going to expedite the process is to accept you're going to have to reach out to Tim Cook's office and have a documented case...
Wish I had better news, but after chasing this issue down for 4 months now I've exhausted every option and indeed am in the process of drafting a letter/fax/email I'm submitting to his office.
Article mentioned above:
https://bgr.com/2018/02/13/ios-new-features-developer-apple-software/
