When you use just the mouse button (shift or ctrl) and hold it, it works for 5?
When you use just the mouse button (shift or ctrl) and hold it, it works for 5?
In Minecraft you changed hand 6 and 7 with mouse buttons 4 and 5. When you use shift or sprint while clicking mouse 4 at the same time, it seems to jump to mouse 5 instead of staying on 4. You can't keep both shift/tab active and click 4 simultaneously—it leads to the unexpected result. Try adjusting your input settings or checking for any mods that might affect this behavior.