Problem with the speed controller
 

Hello. I have a set of FlySky FS-i6X 10CH + FS-iA10B receiver + Cytron SmartDriveDuo MDDS30 - two-channel DC motor controller - 7V-35V/30A controlling two 24V DC 300W motors in a RC lawn mower. When the voltage in the batteries is already low, after the undervoltage protection is activated and the speed controller is switched on again, the mower itself runs as if at idle speed, even when I do not move the equipment and even after turning off the transmitter. I then have to turn off the entire control box. With freshly charged batteries there is no such problem. Failsafe set to 0%. What could be the reason?