RobotStudio event

Machining PowerPac: Failed to Activate. Index was out of range. Must be non-negative and less than

We have had 2 separate cases on different projects in RobotStudio 5.61.02 using the Machining PowerPac where we got the following cryptic message and the powerpac refuses to start on these stations.
"Machining PowerPac: Failed to Activate. Index was out of range.  Must be non-negative and less than the size of the collection. Parameter name: index"

They were working fine one day and then the next, they won't open the powerpac.

other stations open and work fine, but something got corrupted in these recently and it would be nice to restore them to functioning.