Symptoms
The xmlrpcd transaction mechanism is used, order is placed with PlaceSubscriptionCancellationOrder_API with AutoCommit set to No. The cancellation order is placed and processed independently on Rollback or Commit.
Cause
The issue is caused by #PBA-82844 ("Transaction mechanism stops working if we modify CF order order flow").
Resolution
If you need the transaction mechanism to work, change the order flow transition for CF orders from NW to OP back to Manual.