I'm also on Pixel 6 Pro. It signs out every 6 hours and I have to manually sign in. This is with 2 factor authentication on or off. I did a reinstall, which didn't help. The program crashed several times during reinstall and I sent messages to the developer. He responded that he hadn't seen the problem yet, but would check into it.
This is the best Tesla app I have found in the past 5 years. I hope he can find the problem and fix it!