Potentially dangerous wiring in Boeing Co.’s 737 Max jets is the most recent flare-up between U.S. and European regulators, further complicating the grounded plane’s return to service, according to the Wall Street Journal, which cited people familiar with the details.

Experts at the European Union Aviation Safety Agency want certain wires moved to reduce the risk of short circuits, which could disrupt flight-control systems in a worst-case scenario, according to the people. Boeing engineers and senior Federal Aviation Agency managers say moving the wiring isn’t necessary, one of the people said.

FAA head Steve Dickson will make a decision in a few weeks and Boeing hasn’t submitted a formal recommendation, according to the Journal.