There should also be an upgrade for the repeater field add on.
There are troubleshooting suggestions here https://www.advancedcustomfields.com/resources/upgrade-guide-version-5/#troubleshooting
If you are still having problems after trying to fix it you should roll back to V4, instructions on doing this can be found at the above link.
If you continue to have problems please contact support here https://www.advancedcustomfields.com/contact/
