you can drag em onto a 1x1 Grid that is Transparent without any Fog of War (that is great for a fast load time too), grab em by their Roll20 Picture (aka the User Picture, not to be confused with the Character Sheet or Token) and drag em to that Map, this will effectively split them off from the Party, and at the very least minimize any potential damage they may or may not cause. Also, try a Refresh without Cache, I believe FireFox's Hotkey Command is Ctrl+F5, I hold Ctrl during the entire Refresh to enure nothing tries to use the Cache, although some browsers might use other combinations, I think Chrome for example was Shift+F5