hunting a bug on scripted custom properties not being saved

[-hh]

Yes, I got it now. Didn't read exact enough, sorry.

Perhaps your's is somehow connected to the new option
"Preserve stack file version on stacks saved in legacy format"
of the 'Files & Memory' tab of the prefrences?

Would be interesting how your technique and this option interfere?
To know at which point sets LC the stack version when saving?