Report Style Maintenance - Error - Sequence contains more than one element

Trying to get customised ARFrom from E10 to work in E11.

My customised ARForms in Report Style Maintenance were showing a yellow box that said Unknown.

When I click on the box, it turns red and says Error
Message: Sequence contains more than one element.
Correlation ID: f0262e15-9460-4f1a-9a04-ce4b82559301


They are now showing as green and OK.
Must have been a glitch?