I encounter same issue today. I solved it by removing the RTC battery. Need to handle with care on Udoo x86.
I'm experiencing the same thing. RMA has been accepted but still waiting on a reply from customer support to sent the board back (Been waiting for a reply since last friday) Support staff replied to my new ticket (asking for a reply to my old ticket) promptly though. Apparently it's a sophisticated process.
To the OP, try disconnecting the HDMI cable, I have found depending on the TV or monitor used the Udoo will not come out of power save if the cable has been connected and the monitor/TV has also gone into standby. I think that is due to the way some HDMI devices talk to each other, especially the CEC function.
I have this problem today, too. My UDOO X86 worked fine yesterday. As I remembered, this situation has happened once soon after I installed win10 on it, few days after I received the board. I forgot how I woke it up except the reinstall of win10 part. I'll guess the bios is not stable, because now I don't see the UDOO screen.
Weird.... I can access the BIOS now and get into Win10 successfully through Boot manager. Now I think the problem may be from win10 or the Grub2(I have also Ubuntu installed).