+1 to everyone here. While the thread has been viewed thousands of times, there aren't really that many actual posts (and that's across 6+ years) so I wonder if this is a much smaller issue than it seems. Alternatively, I wonder if this isn't the right place to file this issue in the first place. To rule out the latter possibility, I went ahead and opened a ticket to Apple via the Feedback Assistant (case ID FB13585955) where I also referenced this thread. If I hear back from them (not sure how public the feedback tickets are), I'll try to update this thread with the findings.
Even if this issue doesn't affect many developers, I hope Apple will at least provide us with some debug steps. Otherwise, it's just educated guesses, which is very time-consuming (and wasteful).