I have 3 tanks each with an Apex. Personally, I would absolutely replace mine if it went out. I monitor mine to point to things that could lead to trouble. An example would be a new fish that’s either hiding or dead in my rock work or over feeding and food decaying. I have run ozone in all 3 tanks too but I don’t run it now.
I seem to remember when I first set up my Apex that it took a while for the ORP to normalize. I don’t remember how long but I believe it was a couple of weeks or more. Keep that in mind if the readings on yours don’t seem reasonable.