Hello Arnold
That does seem odd. Are you able to set up a staging server for testing? If not, the next option I’d suggest is to clone your site into a sub-directory and hide it from search engines while testing (Yoast can do this).
I’d start by deactivating all other plugins except The Events Calendars & Events Calendar Pro, plus keeping Yoast on to hide from search. Then see if the plugin continues to deactivate itself.
Do you have other backup solutions running or any hosting management tools (ManageWP, or anything provided by your webhost) that might do this?
I hope we can sort this out soon.
Thanks
Courtney 🙂