That Posi Lok WILL let the collar pop off the axle too. Mine popped off just like the CAD, I had to take the clip off the pin to let the collar slip over left axle further and still mine pops off sometimes. The lock on the cable is not very strong. It can bend the rod that roves the collar also. Thsi happened to my PosiLok the first time it popped off.
It's really hard to diagnose your problem with limited information.