Me and my brother were playing on a map, I was on W10, and he was on his iOS device. My bro wanted to play with a controller on mcpe, so we connected a Xbox one S controller to his iOS device, after a while, the controller started to mess up the hot-bar. The game tried to switch slots when my bro tried to but the game just switches between the slot that my bro has tried to switch to to the other slot that my bro didn't want to use repeatedly. The issue still persisted even when disconnecting the controller from the device. AFAIK it never happened to my W10 laptop, only on my bro's iOS device, as I used the controller to play Minecraft before and I never had issues. I hope you can replicate the issue and fix it ASAP.