Costing custom operations seem to be buggy. It appears like once a custom operation is used on a part the operation name gets locked up somewhere that I can't see. Example: I applied the 'Paint' operation on a part but later deleted it. 'Paint' no longer shows up as an option for this part. Another: I made a custom operation specific for a part, but later deleted it out of the part. I was not able to reuse the same name when I tried to put in another custom operation.
Is it just me, or is this a real behavior?