Can't replicate 2016 Toyota RAV4 gurgling noise

My 2016 rav4 has similar issue with right front brakes making grinding gurgling sound. Took to dealer they said no issues. Returning to dealer service again. Problem is intermittent and they said they couldn’t replicate on test drive.

Surface rust can buildup on the rotors overnight if you live in a humid environment but will go away after a short drive.