I had this happen recently as well during a 7.3.2 to 8.0.2 upgrade. Failed first controller over to second, performed the update process. First controller came up with new version, all good. CIFS wouldn't terminate on the second controller so I used "cf takeover -f" and performed the upgrade. It appeared to upgrade fine but after reboot it was running the wrong version.
I ended up netbooting the second controller and pointing it to the DOT8 upgrade image - that worked fine (in the end it did, anyways. IBM swore I had a bad CF card and made me wait until the following day to keep troubleshooting).