Top seed Alexander Zverev was warned for a taking a picture of a contested ball mark at the Madrid Open during more electric line-calling controversy on clay.
The world number two overcame Spain's Alejandro Davidovich Fokina 2-6 7-6 (7-3) 7-6 (7-0) to reach the last 16.
But the success was marred by another row as Zverev was convinced a backhand from his opponent in the 10th game of the second set had gone wide.
The German told umpire Mohamed Lahyani there was a "malfunction in the system" after it was called in by the electronic system.