I'v attached a sample application.
The problem is visible in the first column (Name = "Unexpected Behavior").
Column two and three are added to compare the behavior.
Problem occurs if you bind to a decimal Property and set "Field.Format = string.empty" AND "EditAsType = typeof(decimal?)".
Thank you for posting. I am able to reproduce the behavior you described for the first column formatting.
I have submitted this development issue for further investigation (260745) and have created a private case (CAS-200153-B1F6Y2) where I will provide you with further information.
Please let me know if you need more information.
Sincerely,Divya JainAssociate Software Developer