I am playing a session right now: the sidebar with all the PCs and NPCs keeps resetting and I have to continuously re-add them to the combat, but it also resets their Initiative scores. The Dice Roller and Game Log keep getting shut down by an Error. We are just having an absolute blast trying to play while this keeps happening...

[/sarcasm]

I'm not having the roll error but i am having the combat encounter issue where people at random will disappear from the left har, and i cant readd them.

Its required us to delete and readd the npc or party member several times.

Any tips or tricks to avoid would be great.

 WHen you say "beyond VTT" can you clarify? There's 2.

Maps - the main VTT on here. 

Sigil - a 3D VTT - it is no longer being worked on.

Also ensure 3rd party isn't interfering like Beyond20 extension or using 3rd party VTT like AboveVTT. Despite being designed for D&D Beyond they are 3rd party, not officially supported and known to be buggy at times.