I've personally never heard of this problem before. But I am no expert. Wait for someone like Liam or fox to respond.
From my own expertise, this sounds like it could be a browser problem, network problem, or computer problem on the user side.
It may be helpful for you to give some more details as to what's going on.
Are you using note markers to change the volume?
Also, what computer and browser are you using?
Well anyways, I hope you are able to solve the problem.
please give more information. what kind of computer are you using? what os? does the action of changing the volume freeze or does the sequencer freeze when you try to play notes with different velocities?