`fetchLinks` does not work on sub-documents anymore

We are getting a 502 bad gateway error when using the v2 API to query the documents endpoint with fetchLinks included in the query

I've noticed it only fails when including one specific content type, in our cases we have a product content type and are including "product.slices" in the fetchLinks query params.

All was working as of a couple of days ago so I'm unsure why this might be failing now. Has the api changed? This is affecting our ability to preview/publish and any help would be appreciated.

Thanks