Steps to reproduce:
- Setup a 4.1.4 XEM wiki (Tomcat + MySQL)
- Start and manually import XAR
- Shutdown and replace the WAR with a 5.2.1 or 5.3 M2
- Start, DW kicks in.
- Select "Yes, this is an upgrade"
- Select version 4.1.4 from the dropdown
- Click "Yes, this is it"
- Now the Repair button appears. Do NOT click it.
- Instead, press F5 or the corresponding shortcut key to refresh the page
- You are redirected back to choose "Yes, this is an upgrade"/"No, this is a new install"
- Click again on "Yes, this is an upgrade"
- you will see that the dropdown and "Yes, this is it" are disabled/grayed out, leaving the user no way to continue with the Upgrade.
I personally had to restart my wiki in order to clear this.