iOS devices missing Google contacts (CardDav sync)

I can't seem to find a reason why there are missing contacts from a Google Apps account on various iPads & iPhones. The email account is setup using the Gmail configuration (not Exchange). Mail and Calendar are fine. Contacts are setup using CardDav and I get sporadic numbers after setting up the account.

I have an account that has 1519 contacts in it (through Gmail-web interface, all contacts show up and are accessible).

When I set up the account on the users iPhone 4S (iOS 6.1.1), I only receive 1256 contacts.

When I set up the account on my iPad 4 (iOS 6.1.1), I only got 550 contacts.

I updated both devices to iOS 6.1.2, same results on both.

Set up the account on an iPad 1 (iOS 5.1.1), get 1465 contacts.

I had our enterprise admin create a test Gmail account. I then imported all 1519 contacts from the "real" account into the empty test account.

Set up the test account on the iPad 4 (iOS 6.1.2), now I got 1511 contacts!

I walked away from the whole situation for a few weeks.

Set up the real account on the same iPad 4 (now on iOS 6.1.3), I still only see 1511 contacts.

Tried it on my wife's iPhone 4S (iOS 6.1.3, but a different phone than the original user), I can see all 1519 contacts!

I am beyond frustrated with this whole situation. And worst of all, I have no solution to present to my CEO!

All the tests have had hours to sync all the contacts, so it's not like I was impatient and didn't wait long enough.

Does anyone have any suggestions for me to try? Thanks in advance!