If so, will probably be addressed with https://gerrit.wikimedia.org/r/#/c/199984/

Ya, the id sjabloon_zie is duplicated from templates:

{{zie dp}}

and

{{Zie artikel}}

I made this change,
https://nl.wikipedia.org/w/index.php?title=Sjabloon%3AZie_artikel&diff=43710077&oldid=42670382

Now we wait for restbase to update. In general, the above patch should help these cases.

id affects only data-parsoid and templates are serialized with data-mw .. and I had to scratch my head for a second before being convinced this is an id issue. Selective serialization uses dsr information which is present in data-parsoid. So yes, this is related to duplicate ids.