Something else I noticed is it looks like the screens are slightly different sizes, and I wonder if that is causing the nodes to be re-positioned due to their anchors (assuming Control-based nodes, if using Sprites this does not apply).
Does the same issue occur on a different OS? Like does Windows Firefox and Linux Firefox show the same issue? I'm getting the same issue on Firefox on Ubuntu 20.04 LTS Linux. Have not tried chrome yet.
Edit: Chrome is working fine for me too. Strange, normally Firefox has less issues with web games (in my experience at least).