Approved patches loose there approved status

I've been finding that once I approve patches they can loose their 'approved' status after a day or two.

I've logged the patches I have approved (to make sure I'm not remembering patches approvals incorrectly).
I've also checked the patch approvals I've made shortly after I did them (I haven't found any problems with patches not approving initially).
I'm running build 91002.
For example if I look at patch approvals today, I can see patch number 17556 (MS15-043 aka KB3049563) is marked unapproved.
Yet I've logged that I approved that patch on the 14th - a few days ago.

I almost thought that the patch revisions might unapprove a patch, but the release date for this patch is the 12th.

Any ideas?
I couldn't find anything in the action log viewer.