Errors are being returned when submitting some types of data via the web service to test.musicbrainz.org.
For example, trying to submit puids for a recording,
Content-Type: application/xml; charset=utf-8
<?xml version="1.0" encoding="UTF-8"?>
<metadata xmlns="http://musicbrainz.org/ns/mmd-2.0#"><recording-list><recording id="00e80381-2362-485c-aa47-942ff63f0ac0"><puid-list count="2"><puid id="0281f028-ed20-e974-87a9-8f6785a7c35b"/><puid id="08925bbb-2e07-96eb-8c55-82157a278d3e"/></puid-list></recording></recording-list></metadata>
00e80381-2362-485c-aa47-942ff63f0ac0 does not match any known recordings.
This is a perfectly valid mbid:
Similar errors are also seen when submitting isrcs for recordings, and barcodes for releases. Submitting tags and ratings is fine (with one exception which will be reported separately). The live sever doesn't seem to be affected by this problem, although this hasn't been exhaustively tested to avoid risking polluting live data.