Solidworks 2016 SP4

I have a single variable pitch helix that revolves twice. I made a plane at the end of one of the points and created the cross-section (I'm making threads). When I sweep this profile along this helix, it only sweeps one revolution around the helix. It will not do two full revolutions. I have it's partner thread on a different helix behaving exactly how it's supposed to, so I'm not sure why this one is any different. I was able to force it to work, by making a sketch at the new end, convert entities, and sweep again along this helix. However, it should sweep just once. What gives?

Attached is a screenshot and the CAD stripped down to just the problem areas, with sweeps labeled GOOD, BAD, and MY REPAIR.