I have 2 UDOO x86 boards installed in machines that are used in agriculture. These machines are situated in very remote areas. One of the boards is misbehaving. I configure the UDOO bios to point to the MMC (DF4032), and the board boots Linux ok. Periodically, after power down, the board appears to lose it's ability to boot. Subsequently, when started, it either displays "No bootable device" on an HDMI screen, or the screen reports "No Signal". My only guess at a possible cause is that the small bios / rtc battery is flat, but this is only a guess. Any pointers regarding what may be the problem with this board, will be greatly appreciated. Thank you.
This looks like the same issue as https://www.udoo.org/forum/threads/boot-on-sd-card-works-only-after-ctrl-alt-suppr.8100/ Are you using Legacy mode?