After nearly a month of being waylaid at a maintenance facility, the ferry Wenatchee returned to service Wednesday following extensive tests to determine why the recently renovated hybrid-electric vessel was unexpectedly losing power.

The ferry was pulled from the Seattle-Bainbridge Island route on Aug. 19 after two of its four drive motors unexpectedly went offline, causing the boat to momentarily lose power.

While Washington State Ferries technicians quickly found out what was happening, they spent the last month determining why it occurred, according to John Vezina, the agency’s deputy director.

In short, technicians confirmed what they already knew, that the ferry’s control system communication wires created intermittent instability, which caused the motors to go dark. The motors —

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