There is a persistent bug with the quick-bar/grenade slots (slot 4, usually assigned to HE/Fragmentation grenades, and slot 5, usually assigned to Smoke grenades).
When I select an M18 Smoke grenade from slot 5 and throw it, the remaining smoke grenades automatically shift into slot 4. After this happens, the inventory interaction completely breaks for these slots: I cannot manually drag the M67 fragmentation grenade back into slot 4 (the slot highlights red and locks up).
The only workaround is to drop all remaining grenades on the ground and pick them up again (picking up the M67 first) so they reset to their intended slots.
Steps to reproduce:
Equip M67 fragmentation grenades (slot 4) and M18 Smoke grenades (slot 5).
Select and throw a smoke grenade from slot 5.
Observe that the remaining smoke grenades have shifted into slot 4.
Open the inventory and try to drag the M67 grenade back into slot 4 — the action is blocked, and the slots are locked.
Additional Information:
This issue has been present for at least the last 3 major updates and significantly disrupts gameplay during combat.
Attached Media:
Please see the attached video demonstrating the entire sequence — from throwing the smoke grenade to the inventory slot locking up.