Horrible brake noise while rolling back after cleaning

[TonicPH]

Hi guys, have a little issue with my advice 150 brakes after I had a mechanic to do some work on the bike including CBT cleaning and he also cleaned both brakes and replaced the fronts. Now, after I roll the bike backwards and press the brake, front and rear, they make a horrible noise. At first I thought it will go away but it didn't so I have taken the front brake apart next day to inspect and reclean everything. He did use the CVT cleaner on the brakes which I though could leave a residue on the disc surface? Reassembled everything and it was so much better, however one day later we almost back to same thing. Could it be possibly stuck piston causing the brake drag and noise??
Literally sounds like a bloody trumpet
Sorry can't upload video, link instead:
https://youtube.com/shorts/MMHdU4fHPkQ? ... 1M15FAAWAM
Thank you!!

[TonicPH]

CVT not CBT sorry

[gazmo16]

Brake cleaner evaporates in seconds and is probably what he used so its not that. I'd guess either dirty pad faces which you can clean with a brass wire brush ( like used on suede shoes ) as its sort and won't hurt the pads or possibly sticky caliper pistons which can be accessed by removing the pads then a gentle pump of the lever to expose more silver piston behind the pad. Give the newly exposed piston a vlean with brake cleaner spray then a light smear of silicone brake grease on the piston and gentle push it back in the caliper. As a belt and braces idea maybe a little copper grease on the rear of the brake pad it's self after you clean the area. Not to much and evenly light covering being very careful to avoid any grease on the actual pad side ! . That should cover the usual causes of a squeaky caliper hopefully.