SAFe Scrum Task is stuck at 100 for Percent Complete if it is completed accidentally and needs to change states.
This was happening because of a customized Dictionary Entry Override.
Once reverted, everything should work as expected.
To do so, follow the steps below.
1. Navigate to "sys_dictionary_override.LIST"
2. In the "Table" column search for "rm_scrum_task" and go to the record where the Column Name is "state"
3. In the Versions related list, Right-Click the record with the Source of "System Upgrades: VersionName..."
4. Select "Revert to this version"
5. Select OK when prompted