Running the latest recommended version of Sponge- can't press q to drop items?

I thought this bug was fixed? I am running a Modded Skyblock 3 server [1.12.2 ] with spongeforge-1.12.2-2611-7.1.0-BETA-2931 and intermittently players cannot use Q to drop items [the animation happens but the items stays in hand] and sometimes cannot drag and drop items from their inventory [the item just vanishes].

Any advice?