Ubuntu bootloader disappears every day, how to fix?

Question

linux

Guys, something strange is happening to me.
The Ubuntu bootloader disappears every day.
Now in more detail:
The computer has 4 hard drives, of which 2 are ssds, one ssd has windows 10, the second has Ubuntu 16.04
. You have to boot from a live CD, install boot repair, it fixes everything quickly and the menu appears again. Then, during the day, I can turn off the computer, reboot at least how many times and repeatedly log in under win 10 or Ubuntu. The next morning, there is no choice of OS again (
As far as I understand, I have both disks on which the OS is installed with a GPT partition table. If this is important, then on the motherboard UEFI BIOS (Asus P8Z68-V).
I am not very strong yet in linux. Therefore, I ask you to help and suggest what to check and how to overcome the problem.

Answer 1

Faced such a problem. This is how Windows messes up. If it is not loaded, then there will be no problem. At least that's how it was for me. Google in this direction, the problem is not trivial, you have to sweat. Unfortunately, I can not give exact links and requests, only a direction.

Answer 2

Sounds like your motherboard battery is dead.