Once an item was part of a constraints group it stays poisoned forever. Even across documents.

[Frank Jonen]

This hasn't been fixed since 2017.

[R C-R]

What do you mean by "poisoned"?

Also, what do you mean by "across documents"? How are you moving/copying/whatever the item from one document to another?

[Frank Jonen]

I copy and paste the objects via copy and paste.

Every time I paste an item that has been in a Constraints Group and group it again in another document, that becomes a Constraints Group as well.
It effectively poisons the group.

 

[Wosven]

It would be interesting to get a popup asking about keeping or deleting those constrains when pasting in  an app without this panel.

[R C-R]

1 hour ago, Frank Jonen said:

Every time I paste an item that has been in a Constraints Group and group it again in another document, that becomes a Constraints Group as well.
It effectively poisons the group.

So at this point you cannot remove the constraints from the group you created in the other document? This is what you mean by "poisoned"?