Relationships Sticky Delete(RSD) program

Hello all,

For some reason my listings are not grouped to parent, when I upload the file, there is no error, and in my inventory, all are grouped to parent but on the website are not. That what answer I am getting from amazon support:

"However we found that Child ASIN cannot be added to the parent because it’s blocked by Relationships Sticky Delete(RSD) program. Once the child ASIN is sticky deleted from the parent, subsequent submission between that parent and child will not re-establish the relationship.

For more information refer the help page below:
ASIN creation policy - Variation policy

https://sellercentral.amazon.de/help/hub/reference/G201844590
"

In this policy I am not able to find an answer to what is Relationships Sticky Delete(RSD) program and why asins could be there.
Does anyone have more information about it?
Thank you,Tomas