Yes, torsion axles. Sorry for the wrong term.
And you are correct, the regular spring axles are mounted completely differently, no chance for them to slip.
The funny thing with the torsion axles is that there are holes in the axle flanges to bolt them securely into the trailer frame, but FR simply didn't bother. All I had to do was drill holes through the frame and put the bolts in. I guess that is too much work for them?
I sure hope Prime Time does a better job.