on beta site.

Release where this bug was encountered: http://beta.musicbrainz.org/release/58cbf635-a9f1-46c7-b4d6-d20198772a1b

there are existing solo tenor vocal ARs for three artists at recording level. an attempt to add a date individually to these ARs via the relationship editor causes the solo and tenor attributes to vanish AFTER SUBMISSION once the dates are added (note: the attributes are still applied before submission). a further attempt to restore the vocal attributes in turn causes the added date to now vanish.

affected edits (the latter three are attempts to rectify the disappearing attributes caused by the first three):
http://beta.musicbrainz.org/edit/32309689
http://beta.musicbrainz.org/edit/32309692
http://beta.musicbrainz.org/edit/32309695
http://beta.musicbrainz.org/edit/32309744
http://beta.musicbrainz.org/edit/32309747
http://beta.musicbrainz.org/edit/32309750

collectively listed here:
http://beta.musicbrainz.org/search/edits?auto_edit_filter=&order=desc&negation=0&combinator=and&conditions.0.field=artist&conditions.0.operator=%3D&conditions.0.name=Jos%C3%A9+Carreras&conditions.0.args.0=85233&conditions.0.user_id=407536&conditions.1.field=editor&conditions.1.operator=%3D&conditions.1.name=fmera&conditions.1.args.0=407536&conditions.2.field=type&conditions.2.operator=%3D&conditions.2.args=91&conditions.3.field=status&conditions.3.operator=%3D&conditions.3.args=2&conditions.4.field=close_time&conditions.4.operator=%3D&conditions.4.args.0=2015-03-26&conditions.4.args.1=&field=Please+choose+a+condition

similarly for these other edits for two other artists:
http://beta.musicbrainz.org/search/edits?auto_edit_filter=&order=desc&negation=0&combinator=and&conditions.0.field=artist&conditions.0.operator=%3D&conditions.0.name=Pl%C3%A1cido+Domingo&conditions.0.args.0=23678&conditions.0.user_id=407536&conditions.1.field=editor&conditions.1.operator=%3D&conditions.1.name=fmera&conditions.1.args.0=407536&conditions.2.field=type&conditions.2.operator=%3D&conditions.2.args=91&conditions.3.field=status&conditions.3.operator=%3D&conditions.3.args=2&conditions.4.field=close_time&conditions.4.operator=%3D&conditions.4.args.0=2015-03-26&conditions.4.args.1=

http://beta.musicbrainz.org/search/edits?auto_edit_filter=&order=desc&negation=0&combinator=and&conditions.0.field=artist&conditions.0.operator=%3D&conditions.0.name=Luciano+Pavarotti&conditions.0.args.0=3248&conditions.0.user_id=407536&conditions.1.field=editor&conditions.1.operator=%3D&conditions.1.name=fmera&conditions.1.args.0=407536&conditions.2.field=type&conditions.2.operator=%3D&conditions.2.args=91&conditions.3.field=status&conditions.3.operator=%3D&conditions.3.args=2&conditions.4.field=close_time&conditions.4.operator=%3D&conditions.4.args.0=2015-03-26&conditions.4.args.1=&field=Please+choose+a+condition