I've got some bad news, that may help figuring out where the issue lies though. I just went back to kernel 6.6.106 because of both this issue and several amdgpu issues. I thought it couldn't happen here, but it did. Wherever the source lies, it must have been backported to 6.6. I first set up my FW16 with Debian 12 back in late April 2024, but this issue didn't appear before kernel 6.9, maybe even with 6.10 or 6.11. While I'm not sure when exactly, it most certainly didn't appear before the second half of 2024, most likely only in Q4.
Best regards Richard
