Every time the V5 controller rumbles, either when I incorporate it into my own programming or when I run a competition program, the screen starts flashing red. It doesn’t do this when it’s plugged into the computer or brain, only when wireless. The firmware is updated on both the controller and the brain and the battery is fully charged.
That means the controller battery is low voltage, try leaving the controller connected via its micro USB until fully charged. If after 2-3 hours of charging it behaves the same you probably need to call vex support and explain the issue.
Same problem here , I think it is a bug. We had the controller at full charge and still was flashing red.
It’s happening with our four teams’ controllers too. I had my team’s controller rumble like 40 times in 10 minutes and no battery issues. Looks like one rumble makes the controller think it’s out of juice?
Same here, even when the joystick is fully charged. Would it be possible that it flashes because it senses a voltage drop with the battery as an amount is being used for the motor?
Exactly what I thought when I first encounter the problem. Hope a new update comes out soon to fix this minor but annoying problem
We made some changes to improve low battery detection when using rumble motor, I think it will solve the issues you have all been having, it should be in vexos 1.0.4 which will be available soon.
Thank you! 
Yeah, I tried it on another controller and it works just fine, so hopefully it gets sorted with the update