Sounds odd/unlikely that you would have bad linkages on both rear doors. Have you:
1. Checked that the wire harness' are plugged into the rear door lock actuators?
2. When you lock or unlock using the drivers lock button, does it lock/unlock the passenger side and vice versa?
3. They don't show it in the manual but the door locks do all go through the security control unit, do you have an extra one from your donor to do a quick swap to rule that out?
Don't give up talking to yourself, it can be refreshing at times
