I added Shift End Time to the Volunteer Shift Workers object and the result is a familiar  "Challenge Not yet complete... here's what's wrong: There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: XPISLJFM

This is a new org created for this SB

I had been going down the list of fields to add as shown in the challenge: Status, Desired # of Volunteers, Shifts Taken, # of Volunteers Still Needed, Number of Shifts, Cumulative Volunteers Needed, Shift Start TIme (on Volunteer Shift), Shift End Time, Shift Hours, Total Vol Hours for Shift, Shift Hours (on Volunteer Shift Workers), Shift Start Time, and Shift End Time. 

I was regularly running check challenge just to see what the errors were, and all previous errors were simply that a field not yet added was missing. After adding Shift Start Time the check challenge was that Shift End Time is missing. When I add Shift End Time, either as a formula (Volunteer_Shift__r.Shift_End_Time__c) or simply as a date time field, this error is posted:



If I back out Shift End Time the error is merely that field Shift End Time is missing. 

It is a new org made just for this SB. Anyone have any suggestions on how to fix or get past this error? Many thanks, DG