Also occurring in mod version 3.5.16.

All void upgrades seem to do is double the stack limit. Once a drawer is full no more of that item can be put into the drawer or draw controller. This goes for manually clicking on the drawer/drawer controller or piping/hoppering.

I have tried on server and in single player and have tried the latest release as well as the previous.

I can't reproduce in testing. Void works with manual and hopper insertion just fine.

Are you sure you didn't place an obsidian storage upgrade by mistake? They both use obsidian in their recipe, and the storage upgrade doubles capacity. A void upgrade will put a little purple swirl icon in the corner of your drawer block.

I can't reproduce on a stock SkyFactory 3.0.6. Void upgrades work as they always have.