Auto Brightness toggle missing after water damage CDMA iPhone 4

Repairing an iPhone 4 8GB CDMA Verizon phone that had fresh water damage.

After an alcohol ultrasonic bath everything works except the ambient light sensor and proximity sensor. The auto brightness toggle in the settings UI does not appear anymore.

I have tried two replacement power flex cables with no change in this behavior. Looking at the circuitry related to the proximity sensor and power flex connector there are no missing components, but several had oxidation from the water exposure. These were reflowed by hand with an iron. Still no change.

Anyone have a solution, even for a GSM AT&T model that I could look at?