We very sure that nis_server no longer has code to remove devices from groups.
Here is how we tested: 1. I created a new dynamic group with the filter criterion "name contains '11'". The group was immediately created and populated with 5 matching devices. 2. I then manually added 4 other devices into the group whose name did not contain '11'. 3. I waited for nis_server to process the group. It did and correctly logged that 5 cs_ids are "added" to the group. 4. Once nis_server was done processing the group, it still contains 9 devices.
Release : 9.2.0
Component : UIM - UMP_USM
nis_server-9.1.0-HF1.zip provided which can be required through a Support Case