iPhone 4s Contact Groups not Syncing Deletions

Early 2009 Mac Pro, Mt. Lion, iTunes 11.1

iPhone 4s iOS 6.1.3

I have contact groups that change periodically. After the latest such change today, I find that contacts I delete from groups in iContacts are not deleted from the corresponding groups on my iPhone.

I tried un-checking the 'sync group' checkbox for the group in iTunes, and syncing

(the group disapeared from my phone)

then re-checking the group checkbox and syncing again

(the group came back with the deleted contacte still there!?!).

I have a workaround:

I can delete the group from iContacts, sync, recreate the group in iContacts and sync again. This is okay if the group only has 10 or 15 members, but if I have to do this to a group with hundreds of members, it won't be pretty.

Meanwhile, I am left with;

Contacts I add to a group appear as part of the group on my iPhone after I sync, as expected.

Contacts I delete from a group remain in the group on my iPhone forever.

Can anyone point me at a fix for this issue?