In the 28.7km Crinti test on SS2, Mathieu Arzeno, Patrik Flodin and Sepp Wiegand all had trouble, with Flodin later apologising for hindering rally legend Francois Delecour.
Delecour claimed he lost over 20 seconds after Flodin suffered a puncture 6km from the finish.
But there were no such problems for Mikkelsen, who won his second stage in Romania to move into a 57.4 second lead over SKODA team-mate Gergely Szabo.
“It was long and tricky but better than we expected from the recce,” said the Norwegian. “I tried to keep clean and tidy to avoid the rocks.
“We’re not overdoing anything, driving as we planned and I’m very comfortable.”
Back to the troubles, and Arzeno ground to a half at one point, Wiegland lost over a minute thanks to a puncture, while Flodin suffered a similar problem.
Despite his problems behind Flodin, Delecour is third overall, just under a minute shy of Mikkelsen.