So far this has always happened in creative mode, so I'm not sure if it happens in survival but I have a strong feeling it probably does. When I choose an item in the item list, for example cobblestone, it usually takes up one space in my toolbar. But the bug is that instead of taking up one space, it takes up 2 or 4, or at most 5 spaces. And when I try to choose another item, it takes up all the spaces once again so I can only have 4 items in my toolbar at once. If I throw the item on the ground, all of those items in those spaces go too but the process repeats again. This irritates me a lot and I would really aprreciate if you could fix this bug. This has also happened on multiple other devices including, my friends', my sister's, and many others. Thank you very much!