Hello,
I just did bunch of updates on my site (still under development) and afterwards got an error when editing a page with Oxygen. See attachment. When i deactivated your plugin, and relaunch the editing of the same page, no error came and i could continue my work properly.
I currently use ASP 4.19.3, Oxygen 3.5, and WP 5.5.1. Thanks for looking in this issue.
Let me know if you need access to my site, i will then give you those details.
Best regards,
JL