Certain slots will prevent you from selecting other slots with 1, 2, and 3.

First bar first slot will prevent you from switching to first bar.
First bar second slot will prevent you from switching to second bar.
First bar third slot will prevent you from switching to third bar.

version 1.10.3, minecraft 1.20.1, forge 47.3.10 here, I noticed the same bug, I think it may be happening because the game tries to move to that slot before inventorio intercepts the input, and seeing as it's already there there's nothing for inventorio to intercept?

ETA: the same is true when trying to switch to the same position in one of the other bars (i.e. if you have 1-1 selected, you can't switch to 1-2, 1-3, 2-1, or 3-1 for example)