@Pedro Moita , something is happening on the client machine which is triggering some PnP action which is reinstalling the queue and plopping down the MS driver.
If the printer is shares from a different machine, I would do the trick that has been working for over 25 years.
On the client system, create a local printer using a Local Port in the format \servername\sharename. Set this up with the vendor driver.
This should be redirected in the TS session so the files from teh Remote Desktop Server is copied back to the client system and then on to the machine sharing the printer.
In this configuration Windows should not be making a determination to replace the driver.
You can check the C:\windows\inf\setupapi.dev.log on the client systems to determine why Windows might be changing the driver for the connection to the share.
Thanks