UPDATE : I spent my day today updating software and installing version 2020 so that I would have 18, 19 and 20 to run tests for this issue. (We were currently working out of Fabrication CADMEP 2019)

I pathed all three versions to the same database where the issue occurs.

In the 2018 version of Fabrication the database acted as it should. Copies of the service templates were made correctly and I was even able to delete the incorrect copy that had the wrong items in it without issue.

In 2020 the same issue occurred as in the original screencast from 2019. The service template was copied with the wrong items and when attempting to delete it a different template would get deleted instead.

I did notice that when selecting the current service template the menu was a bit different in 2018 vs 19/20. 2018 just lumped all service templates into one list vs 19/20 which sorted them by the associated group. Not sure if that has anything to do with it, but it stuck out to me right away.