When disabling automatic updates you'll run into problems when new clients join.
The entities won't be updated correctly leading to weird results.
To overcome this you either need to workaround a lot or enable automatic updating for a short time so the model file and the like are adapted. After a few waits, disable all automatic updating again. This was my approach for the last time I tested MP.

It would be nice to have another implementation which takes care of removing disconnected client player entities and initially updates player entities of newly joined clients (even when further automatic updating is disabled) without having to fiddle around with such tricks and workarounds.