Standart UCI_Update generates Insert command in the backend

Hello community,

I created a SCIM sync project using the SCIM connector in the synchronization editor. In my DEV environment everything is working correctly. 
I used transport packages to transport the connector to my TEST environment, the problem I'm having is that an update is executed as insert.

Test case performed:

1. Perform an update of for example Firstname on a CSMUser object.
2. Witness that the CSMUser Provision job gets triggered
3. Check the UCI object that it is correctly updated.
4. Witness that the UCI_UCIUser_Update process is triggered
5. Check the target system by browsing the system. --> Error no update is received
6. Upon further checking the LOGS in the sync project, I can see that the UCI_UCIUser_Update process has rather triggered an INSERT instead of an Update
7. This happens in my Test environment, but not in my Dev environment.

To make sure nothing was wrong with my transport packages, I:

1. Deleted everything that was imported using packages.
2. Re-created the SCIM and UCI Sync projects from scratch
3. But am still witnessing that even though I am updating data, an INSERT is generated according to the Logs.

Any idea what could be going on here? I'm using One Identity V9.0 with cumulative update 1.