Fatal error after upgrade

Uninstalled then rolled back to previous version clicked upgrade again and got this one

MailPoet Error: MailPoet has detected a dependency conflict (\csstidy) with another plugin (/home/(myserver)/public_html/wp-content/plugins/fast-velocity-minify/libs/CSSTidy/class.csstidy.php), which may cause unexpected behavior. Please disable the offending plugin to fix this issue.

rolled back to previous version again all is well I will not update !!!!! ?? atleast till ya fix it

Same conflict with Mailpoet 3 here. Exact message in the dashboard is: MailPoet Error: MailPoet has detected a dependency conflict (\csstidy) with another plugin (/var/www/XXX.com/wp-content/plugins/fast-velocity-minify/libs/CSSTidy/class.csstidy.php), which may cause unexpected behavior. Please disable the offending plugin to fix this issue.

Mailpoet fails to run when the latest version of FVM is loaded. Mailpoet has a potential fix here:

https://beta.docs.mailpoet.com/article/204-resolving-conflicts-with-other-plugins

Right now I have disabled FVM, but may consider a rollback, if this goes long.

I went ahead and tested in rollback, using WP Rollback. It went fine in my staging environment, so I also did the same in production.

I have done a rollback on 2.2.8 with some minor bug fixes only, and will be looking at the other issues at a later time. Sorry and please update.

Seems like some other plugin is including the CSSTidy library, hence it conflicts with this one, as it would be a duplicate.