[Savage GT]

If it only happens when the pit garage lights are on, then logically, that must be the culprit.
Are the pit garage lights powered from a separate supply to the timing lights ?

As you have swapped the lane sensors and bridge lights around, and the same lane plays up, try temporarily blocking the pit garages lighting at the rear so that does not shine near the timing sensors.
If that cures it, you may need to reposition those.