tamte
that's really an odd behavior and you should probably submit it as a bug as it's rare that something downstream that's only reading the attribute would affect upstream behavior in this way
i reported the bug , but its not a bug:
This is the answer from side FX :
Hello,
Our developers comment:
You CANNOT animate the number of multiparms using the multiparm field. This includes driving it from geometry attributes, etc. This may appear to work where it can statically resolve a constant value, but cannot work as soon as you end up with a for each loop where it varies during execution.
Native Verb-based nodes that have multiparms can be overridden with the Parameter Override option, where the parameter override is built by a vex wrangle to override the multiparm. Attached shows an example building such an override for the Add SOP.
best company ever , in only 24 hours they send me an answer.
I upload the file , if someone wants to know the workaround