Are your motors definitely configured for the correct side? Caught myself out the other day when I reversed the drive train using the arrow, but of course left is then right and right is then left so needed to change the motor ports to reflect…
Nothing changed in the program from when it did work correctly except that vex code blocks updated along with Brian firmware. After that is when it went haywire.
I’ll try to get a screenshot but it’s on a different computer.
We had this problem on our bot, the problem in our case was that the gyro doesn’t work upside down (LED facing down). We flipped it over and it worked fine. Dunno if this your problem, but it worked for me.