The solution was to give the second copy of the action block different ancestry, but how, since there isn't an unadopt function on the CSE.
The workaround was as follows:
- scope a subset containing the ABs that you want to unadopt
- download the subset
- generate a new (temp) model on the CSE from the subset so that the ABs in the new model have new ancestry
- selectively adopt just the business systems in the new model to the old model
- selectively adopt the ABs in the old model to the ABs in the new model so that the ancestry in the old model changes
- delete the new (temp) model