2001 Aztek Help!

I love my Aztek despite the many repairs that have been made to it, some under warranty some not. Recently, I had to have the transmission replaced but prior to that there was an issue with the vehicle thumping into gear as I’m driving. I believe this is after it gets hot. It seems like it’s changing gear at the wrong time. I don’t know if this is the reason for the transmission being replaced but I don’t want to have to replace it again any time soon. Has anyone heard of this issue and what needs to be done to fix it.