weird reolution bug when opening inventory

when i open bags/inventory my resolution switches from 16:9 to 4:3

its really annoying and i cant find a way to turn it off.

when i asked global chat i was told to solve it by putting a finger up my ***

cool community for sure!

but for real how do i fix it?

it confuses my brain when the screen switches like that and its not neccessary at all for this to happen