This guide will help you with troubleshooting issues with OptimizeCheckouts
Before you start, you must do this first
Turn off other plugins on your site. This is the first thing our team will try, and you will save yourself a lot of time if you check this first.
To do this, go to Plugins > Installed Plugins and deactivate the other plugins on your site one at a time. You may wish to install a maintenance mode plugin on your site first to let your customers know you’re making some updates.
After deactivating each plugin, you should recheck and see if this resolves your issue (remember to clear cache each time first)
Turn off JS Concatenation in Jetpack Plugins