After the problem is solved, but thought I'd pass this on. "Normal" machine threads are cut at an angle of 60 degrees, so when you print, you've got a lot of overhanging perimeter. Also as the thread prints, each layer shape in the threaded area is exaggerated at the farthest overhang (look at a layer in the slicer). The result is a risky edge that often curls up (at least mine do). One answer is more cooling. Another is to lower the filament temperature as much as possible, because it improves cooling.
If I am3D printing both the male and female threads, I modify the thread profile to eliminate the 60degree bit. The easiest way (for me) in Fusion 360 is to make a male "tool" body to cut female threads, and a male "tool" body to cut the female threads and use those tools to subtract out the material I don't want. Tweaking the threads is the "big trick", easiest explained by an example of making a threaded hole. I make the tool by creating a cylinder that fills the hole that will be threaded this is a new body in F360 lingo. Then I scale that body to 66.666% along the axis (make the plug shorter). Then I use F360 to apply standard threads to this body. Then I scale it again in along the axis, this time by 150%. Now it's the length of the original plug and the threads have been stretched so their thread angle is close to 45 degrees, an easy overhang. Last step is to do an F360 "combine", but cutting, not joining. Also, don't delete the tool bodies. The female threads in the hole are done. Now take the tool and scale it again, this time in the X and Y dimension. The scale factor depends on the the diameter of the plug. I shoot for a reduction of about .2mm per side, so maybe 98% might be typical. This scaling makes the male threads slightly smaller so they'll fit better. Now do another f360 combine, but joining to a stub on the male part. Done. I think it takes longer to write how to do it than doing it.
