With testing I have a lot of machines that are still showing up in Patch Management after I have removed them from RMM and uninstalled the software from the machine. One machine is showing up 3 different times because I installed the software 3 separate times.
Regarding the duplicate entries issue, this has been resolved with the latest PM update, meaning that the endpoint will no longer be duplicated if re-enrollment is attempted on the same machine.
The duplicate entries that you are seeing must be older entries. Please remove them and let us know if duplication occurs again.