I think I figured out my issue. I updated customer addresses in three stages. Create new addresses, update existing addresses, and delete address. The first run would work just fine because there were no addresses to update. And on a second run when it hit the update stage it would load the address subrecord and check the values and if it did NOT need an update it just went on to the next address. And here was the problem, I never called customer.cancelLine(), which I think caused the last line's subrecord to remain in an 'open' state, so when a new address was added to the bottom of the list it was actually editing the addressSubrecord from the line above. I've updated my code to update addresses first and to make sure to cancel any line not in need of an update.