Helical screw in assembly

Hi

I have a screw and nut in assembly.

I use 2 component placement

1- cylinder : connect screw and nut axis

2- slot : connect one point  nut  on helical curve on screw

It's right

Now, my problem:

the placement is unstable, when i regen , the nut move oddly . small movement.

but that's not the most serious

When i use this assembly screw / nut in another assembly : now screw/nut is sub assembly.

And when i use snapshot to define a lot of position of mecanism, when i regen (go out snapshot window) the sub assembly don't keep the snapchot position.

If i disable the slot connection (directly in placement component, not in the snapshot window), it's OK , the snapshot position has keep! but the position screw/nut is not good because the tooth has interpenetrated

It is possible to keep a snapshot position when go out snapshot window, and the slot connection stay on?

or it is possible to define a snapshot as default position ?

Thanks