Nested loops can be tricky, and you want something like this(one of n8n members solution):
Summari :
In your inner Loop Over Items node, go to Options → Reset → Expression.
Use an expreession like:
{{ $prevNode.name === ‘Your Outer Loop Source Node’ }}.
Ensure the data flow from the inner loop’s “done” output does not overwrite or replace the outer loop’s Dat for the next guest.