I have a small simple board with 4 push buttons. The 4 lines are pulled hi in the micro and pushing the PB should pull each low independently. However, On 5 out of 16 new production boards when I push the MENU button the unit acts like I also pressed the ENTER button. I can see the ENTER line drop from 3.3V to 1.4V like there is a short between J4-1 and J4-2 but I don't measure a short. I also see the PLAY line get pulled down to ~3.1V when MENU is pushed. On the working units these lines are steady 3.3V. If I measure from the PB1-1 to J4-1 I see 33 ohms and same for PB2-1 to J4-2 so the resistor network IC seems fine. The good board measures Mohms from J4-1 to J4-2 and the bad boards are measuring about 200k!
The scm section in the dotted box is the push button board. The mating connector and ESD protection is shown for completeness.
I am suspecting board contamination may be the cause but didn't think board flux/residue would so drastically affect such a non-sensitive circuit.