Data Juggler (2/21/2021)
If you read this page, a couple of sections down there is an example on how to unregister a call back.
https://wiki.reallusion.com/IC_Python_API:Linked_Controls
I found this after I read your post.
I had some problems using a timer where IClone kept crashing so I gave up. I may retry your block 1 code.
Thanks Data Jugular
It was a missspelling on my part so all good now.
Chris.