How you find that bugg:
Create a Scoreboard with that score:
minecraft.used:minecraft.map
now set it as sidebar so you can see it
Give yourself Multiple Maps in Slot 1 and
1 Map in Slot 2
Now Just Right click on Slot 1 and you will see the Score going up
but if you do the same with only 1 Map nothing happens

Multiple Maps = Score Raises
Only One map = Score doesn't React to it