Inconsistent run-on can be caused by several issues. The most common cause is when the needle roller bearing inside the torque sensor starts to fail and becomes stiff or drags. There is a setting in the Brose factory software to turn this assistance, or 'ghost assist' off, but your normal bike shop would not have this level of software.
Fist I would drop the chain off the front chain ring and try holding the chainring and turn the pedals slowly backwards by hand to feel if there is any drag or stiffness between the rotating crankshaft and stationary chainring. If yes, take it to your nearest eBike Motor Centre partner, if it's free, check the rear wheel freehub is also turning freely. If this is is also very free, it could also be a calibration issue with the torque sensor inside the motor. This can be changed too.