Possible leak?

Just got a kegerator and corny keg all installed with a stout sitting inside. I’m setting the PSI to 30 for 12 hours then drop to 10 for serving. It keeps dropping to 20 psi after a few hours. I sprayed soapy sanitizer every where to see bubbles and there are non.

I notice the nob that controls the pressure it lagging and I have to turn it several times just to crank it up. It doesn’t go up in increments but after 3 turns will jump 10 or so PSI. Could this be the issue?

with mine, I find that it works better if I first overshoot then back it down to desired pressure.  YMMV

It is most likely the regulator. Many regulators that come with the kegerator’s today sadly are not the best quality.
The diaphragm does poorly for home brewers that need to change the pressures. Inside the regulator is round rubber diaphragm and a seating mechanism normally with a pin style actuator. With the Co2 OFF. Open the regulator by unscrewing the Cone bonnet, careful removing  the diaphragm and spring.( make note on how the were installed)
With the Co2 WELL-secured turn on the Co2 valve. Nothing should be coming out of cavity.
With the handle end of screw driver press on the pin to make the Co2 pop out a bit do this 3-4 times. The seat below the pin should close tightly each time. If you get some leakage this well may be your problem. I’ve even seen some regulators that are inside the cooler, have the spring rust and seas up.
Good Brewing

Same here.