Drive motors will pull the most current on your robot.
I see you as having two problems.
- Resistance through the main power input to the PD Board
- Bridge converter is not plugged into the boosted 12V output.
1. Driving the drive motors at 25% output shouldn't drop the battery voltage enough to cause the 12V-to-5V converter to drop out. However, it doesn't take much. Looking at AndyMark, the converter has a voltage input range from 10-30VDC. Having your battery voltage drop below 10V to cause the Dlink's voltage supply to droop below 5V means you either have a loose connection, bad breaker, or a bad battery. This is assuming you're using a charged battery.
2. If you're ever dropping connection because the Dlink resets, then you don't have the 12V-to-5V converter plugged into the boosted 12V output.
Follow the steps on
ScreenStepsLive.