Moved to ePO for a better response.
It is EPO version 5.1.1 (build 357)
You can remove extensions via the entry in the Software Manager.
If you select RSD in the product panel at the top, and find the management extension in the bottom panel and select "Remove" on the right of the row.
I tried that and it says failed when I do it that way or in the extensions section as well.
It leaves in the RSD queries which can't be removed once it says failed.