It's what GOG's own website uses, so, unreliable or not, it's actually supplying the prices you're seeing when you purchase things or look at product pages.

Thanks. I indeed see them using the multiple ID calls for things like "buy series" and "users also bought". Pretty hopeful!

I didn't keep track, but I think it happened every crawl, which is more than 1 in 100 requests.

FWIW, I haven't encountered this at all in my API calls so far (and added explicit logging for it, so it wouldn't escape my attention).

For anyone using the v2 games API, GOG is changing certain fields. The changes of the last two days have been:
* _links/iconSquare has been removed after being empty for a while
* _links/boxArtImage may be missing instead of being empty
* series may be missing instead of being some falsy value. I don't remember what is was previously, probably empty object, but from the code it could also have been null or false.

It was null on some entries at least. Sigh, hope it doesn't turn into a major change... API payloads aren't expected to change without a revision in theory :/.

Edit: And indeed my scan script failed because of missing series fields now, lovely. Seems like _links/store can also be missing now. Equally lovely. It makes for a lighter payload at least, but the change is a bit disruptive.