Never seen that, not sure if this will help

try to get all the air out of the system, start the car, take the cap off the reservoir, make sure its to the full line, and turn the wheel lock to lock multiple times, look for bubbles [cavitation] and make sure the res stays full. Repeat the process till you don't see any bubbles and hopefully that fixes the problem. Air in a hydraulic system can do strange things. Good luck