I have about 12 prototype boards that have been working for about a month.
Three of the boards then failed and all failed in the same way. The symptom was that the board stopped booting.
I found that NVCC_LVDS2P5 was at about 1 volt and should be 2.5V. In this design NVCC_LVDS2P5 was powered from the PMIC VGEN3 output voltage (2.5). All other imx6 power rails requiring 2.5V were powered from VDDHIGH_CAP from the i.mx6 processor. I disconnected the LVDS rail from the PMIC and connected to VDDHIGH_CAP. The board then booted properly but was unstable would would not boot reliably. I measured the VDDHIGH_CAP voltage and it had dropped to about 2V. Any known reason for these voltages to drop like this?