Another oneplus 6t user here who keeps experiencing the same issue on this new phone (also happened on oneplus 3t).
You know it's gonna happen because the buzzing sound starts. Then you get the freeze. The game is unresponsive until you close it. Doesn't matter how clean your phone is as I've had the crash on a brand new factory reset device where swgoh is the only app on there.
I thought it might be something to do with the game losing sync with the server but not sure it can be as on closing the unresponsive app the server counts your battle as a loss so its still reporting that ok. I've just lost out on rolo shards in hoth as the event now shows as complete doh! (don't suppose there is a way players can have this sort of missing shards thing recompensed?)
Quite annoying as I'll now have to wait for the next hoth rebel tb which probably won't be for another couple of months
Anyways good luck everyone.