The Mars rover Curiosity appears to be suffering intermittent short circuits in its robotic arm, which could limit its drilling of rocks, NASA said on Friday.

The problem cropped up on Feb. 27 when sensors on the rover observed a surge of current. The rover automatically stopped what it was doing and waited for further instructions from Earth.

Curiosity had been in the middle of shaking a sample of rock powder, preparing to deliver it to an onboard chemical laboratory. That same process was used without a problem in five drilling efforts in 2013 and 2014.

In a first test after the power surge, the rover retraced its steps up to the shaking. There were no problems.