See https://community.metabrainz.org/t/is-there-a-parameter-to-include-more-information-in-searches/419673. Searching for https://musicbrainz.org/release/254e53fc-c460-4d38-8f59-2effa6e4e33b like https://musicbrainz.org/ws/2/release?query=reid%3A254e53fc-c460-4d38-8f59-2effa6e4e33b&fmt=xml returns an XML document without release event information.

I suspect that that's due to https://github.com/metabrainz/sir/blob/33c9f22e25fe3818f12509e96b43c7036002a42a/sir/wscompat/convert.py#L1049-L1061. That's processing release events in country_dates (the backref created by https://github.com/lalinsky/mbdata/blob/fd6a391d3d1c0a3085904ae65a50129a34cd1a51/mbdata/models.py#L6265), but not the ones from unkown_country_dates (https://github.com/lalinsky/mbdata/blob/fd6a391d3d1c0a3085904ae65a50129a34cd1a51/mbdata/models.py#L6282). At the moment, the above release doesn't have a country attached to the release event.