I would suspect the hoses to the front calipers have delaminated and are not letting the pressure release. The next time the brakes stick,crack open a brake line fitting at the master cylinder that goes to that wheel, if brake fluid shoots out under pressure it is a bad master cylinder. If not, open the bleeder valve on that caliper. If that releases the brake it is bad hoses. If neither of these release the brake it is a bad caliper-again.
The fact that your mechanic hasn’t figured this out means I would advise you to start shopping for a new mechanic.
I’m concerned about the OP’s remark that the car was moaning even in park. This says something other then brakes was causing the moaning (and I’m counting the power booster as NOT part of the term “brakes”)…
The moaning is when the car is in park AND when you take your foot off the brake pedal. Before and after there is no other sound.