Is there any limitation in how quickly/often I can change a 6V DC motor direction of rotation?

I have a 6V DC motor, which needs to change rotation direction every 5 seconds or so.

The motor is powered and controlled by an Arduino. Arduino is providing approx. 8.5V and I’m using PWM control to lower the average voltage to approx. 2.5V, which is giving me the motor RPM I need. Motor is similar to this one (micro gear motor) and I discussed the suitability of PWM in this thread.

This motor was previously running for a long time on a bench DC power supply. But when I started it using Arduino it stopped working after less than two days. When I connected it again to DC supply it started working normally, across a range of voltages. So I don’t think there is a mechanical failure.

I’m now troubleshooting what went wrong. While I’m checking my Arduino control code, I also wanted to ask if you can think of anything electr-mechanical that could go wrong with this setup (I’m not an electrical guy). The control sequence is very simple – a loop that will issue direction change command at set interval. So I’m thinking about windings, impendance, current, or whatever. By all means, you’re free to have a laugh at my silliness but please bear with me. I’s appreciate any advice.

Thanks!