Commands cannot be assigned to that key issue

This issue has plagued me for a very long time and seems to come and go and I am not sure what the fix is. Basically, I have my hot bar assigned to various alt+, ctrl+, and shift+ numbers.

At some point, however, certain key binds stop working. When I go to the key bind options, they are assigned properly, but when I remove the key bind and try to reassign, I get a message that says "Commands cannot be assigned to that key", which is bizarre because the previous day the key bind was assigned to that key and working.

What is weird is it only impacts some of the numbers. For example, this issue first impacted my ability to assign ctrl+1, ctrl+2, ctrl+3, ctrl+4 and ctrl+5, but ctrl+6-0 worked just fine.

Now, shift+1 through shift+7 won't work, but shift+8 onward do. Anyone else get have this problem?