I found this weird, and random bug with UserInputService
Basically if the player holds shift (only shift) and presses 2, the input for “2” doesn’t work, if the player presses any other key e.g. 1, 3, g, etc, it will work, but not for 2. This only happens when the player is holding shift also.
I’ve also experienced this bug before with a custom toolbar system I was making. Never figured out why it happens, but it may be related to some custom key binding that is only in studio.
If you print out the keycode name does it read as !, @, #, $, etc… ?
The event just isn’t fired, nothing prints
No clue then, that’s weird though
this has been that way for a Loooooong time, Every game ive ever played (2k+) has had this issue, ive gotten used to the 2 key not working by now so i almost never use anything in my inventory at that slot 
maybe check the core scripts?