I set up a cursed earth mob farm in the nether. The farm has two beds of cursed earth. It spawn mobs when I am standing there. They are moved to diamond spikes with analog fans (trap expansion) on one bed and express conveyors on the other. The drops are collected by a vacuum hopper. There is a chunk loader that covers the entire farm. When I leave / log off my overworld base can still get blaze rods from the farm meaning it stays loaded. When I go back to the farm no new drops have been made, but there are usually ghasts stuck in the farm (other issue). It seems as though the farm is still spawning mobs, it's just not moving them or killing them or collecting the drops. I am unsure why it doesn't function as when I am there, it does.

Using V1.6.3 BETA on All of Fabric 3. I will try updating the mod on my client and server and see if that resolves the issue as I just noticed it is out of date by quite a bit.

This is still an issue on V1.6.7 BETA.