Hey, this is a known issue. The scroll position resets when switching between chats, and the bug has been coming back on and off for quite a while.
Main thread on this: Chat view scroll position resets when switching between conversations
The team is aware. I added your report to help raise the priority. Unfortunately, there’s no workaround yet, and I don’t have any timelines to share, but we’re tracking it.
Let me know if you notice anything else.