Hi Frank,
I seem to have the same problem. Because Autoptimize broke my site (rendering failed) I tried to uninstall/remove the Plugin. That does not work. (Error message : Verwijderen van: Er heeft zich een kritieke fout voorgedaan op deze site. Meer informatie over probleemoplossing in WordPress. mislukt)
The site itself does not seem to have any problems anymore after deactivating the plugin, but working with the Elementor editor is extremely slow. What to do?
I followed your (logical) suggestions:
0. reactivate autoptimize
1. go to settings -> autoptimize and at the bottom of that screen click on “save changes and empty cache”
2. when that is done check if cache size indeed is low (below 100Kb)
3. de-activate autoptimize
4. try removing it
Unfortunately, that does not do the job. I did not recieve an automated mail from WordPress with a specific PHP error.
However the PHP error I get in de debug log is the following: Deprecated: ltrim(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/wp-includes/formatting.php on line 4494. Which is not useful in this case I presume.
I also reactivated Autoptimize with all settings unchecked, saved it and then tried to remove it. Did not work either. What to do?
Will deleting the Autoptimize plugin directory help?