Why are records with Transaction Action (TNAC = UB and TNAC = UA) created in the F1201Z1?

We are using a third party software to track maintenance on our vehicles.  When changes are made to these assets, the changes are interfaced to JDE.  This has been working for us for the past 5 years.  I made a change to the application that loads the F1201Z1 but I did not modify the code that inserts records into the F1201Z1.   Now when I process the records using the R1201Z1, the records that I inserted process successfully and EDSP is updated to a '1'.  Two additional records are created in the F1201Z1 for each asset.  One record has TNAC =