In the last days I have been working with the motor described in the title, everything was working fine but I have started having problems with the motor.
The problem is that when I connect its power pins directly to 12V (red and black) the motor does not rotate continuously at 100 rpm as it should, its speed is not even half. When measuring with a multimeter the powered pins give me values between 5.45 and 6.3 V which makes the motor turn intermittently.
It should be noted that I am feeding the motor with a source that exactly provides 11.97V and 500mA. Also, the motor was working fine since it could control its speed by pwm, suddenly the problem started. Did it break down?