regardless, there's no way the FM direct adapter caused the issues with the FM tuner,
You're saying that it isn't possible that the adapter has failed and did something it wasn't designed to do?
hey've been well documented here and elsewhere
I certainly haven't seen that, and I read a lot here. There may be a couple failures, but nothing widespread. (That I have seen.)
3) the adapter causes no issues with any other cars (or they wouldn't be selling it to begin with)...
The particular adapter that you have, or just the same model? Yours could be bad. It could also be that the electronics in the Model 3 are more sensitive than what other cars have.
There are plenty. Here's one thread on it (there are many more but I'm on my phone and don't have time to link them all, a simple Google search for model 3 FM issues will find them though):
FM radio stopped working
And at least a couple of those people report having hooked a XM radio adapter to it. Hmm... Could that possibly be related?