When using the page system for the backpack in my game, specific slots (each page has a UIGridLayout that orders the items) will cause the page to change, making it impossible to select some items. This first appeared about five months ago, but I was able to fix it then by making each page that isn’t on screen invisible. After about a month ago, the page system was acting up again, and the problem was caused by my fix for the first time it was buggy. I stopped making pages invisible, and it started working again, but the old bug that caused the pages to change with gamepad input (set to false) came back.
Try making a page system that has a grid of buttons on each page (using a UIGridLayout) and set the page’s “GamepadInputEnabled” property to false. In my case, this still allows the pages to change with the gamepad.