HB-100 Line Pulling Hydraulic Disc Brake Calipers, Mechanical Disc Brakes for MTB, Mountain Bike, E-Bike and Electric Bike 2PCS Front/Rear Black

For quick fix, put blue loctite on the bolt. For semi permanent upgrade switch your calipers for line pull hydraulics. It's almost like hydraulic brakes without replacing whole lines. It activates with a cable but applies pressure with hydraulic pistons. Long term consider upgrading to full hydraulic brakes. Just find ones with same electrical motor cut off sensor.