This is happening to me as well, my apps lag when exiting out and in some cases I have to force reset my phone to get it working again.
Will Android 10 come out soon on OnePlus 6t devices that come from T-Mobile? Ive been waiting for way too long, no update notifications at all.
I haven't received the update yet, and Android 9 seems really unstable right now, I don't know if it's because I don't have Android 10 yet or not but...
Flash, because when you chose OnePlus, you unlock the speed, Flash is speed. That's what Oneplus is all about!