Agreed. I tired 8 times and only got it to work once in the hangar today. I tried originating the request from both the PFD and MFD. No joy. It was nice when it did work. I was able to to fill the entire screen with the plate.
I've seen fluctuating oil pressure caused by bad grounds and also by lack of a restrictor fitting (https://www.aircraftspruce.com/catalog/eppages/oilfuelflow05-11908.php) on the oil pressure line going to the sensor.