I am sweeping a profile around a helix, and using an assembly to connect the parts end to end and verify that the sweep isn't twisting or doing anything weird. I've always struggled with this because I get inconsistent results, but I finally proved that it's actually a software error and not my own.
When I define the helix as having 1 revolution, the result is good and the sweep doesn't twist. Same result with 0.75 revolutions, 0.5, etc.
But, there's a hard limit. At exactly 0.14 revolutions, the sweep changes from a helix to a flat circle(tilted). My assembly confirms this, because what used to look like screw threads is now just a donut.
I can't tell what the root cause of this is, whether it is the helix tool or the sweep tool, but I can tell you that if you're having trouble sweeping around a helix, it's probably a software bug and not your own modelling.