Those of us using Firesticks might have noticed certain channels which use interlaced video such as the BBC channels cause the IPTV app to crash. This issue has been outstanding for over a year, but it looks like Firesticks are finally now receiving new firmware which fixes the issue. It looks like they are doing a staggered roll out, so not everyone has the latest firmware yet.
https://github.com/amzn/exoplayer-amazon-port/issues/94#issuecomment-675371120
Finally, was driving me nuts with European channels causing my player and sometimes Fire TV OS to crash completely.
edit: have two 4K Sticks, one just received the update 6.2.7.3 .
Edit #2: Compared to my other Fire TV Stick with old firmware, I can confirm that crash is fixed now!