After completing all of my probational requirements, I received a letter scheduling my case for hearing for "review of probation". I was instructed by my probation officer that I would be receiving a discharge letter at my last appointment. Instead, I have received a letter for hearing from the Judge. Is this Normal for DUI? Or am I going to find out something horrible?

Where? In NY (where I am) there is often a hearing so that Judge can make sure that the person who was convicted understands the rules going forward.

It may be normal, for your court, but since the PO did not mention it, it sounds like it is not.

Is there any reason, or anything happening that could cause a issue