I don't have a ready solution, but a couple thoughts come to mind:
Does your machine have a battery backup for the BIOS? Often this is a CR2016 or CR2032 cell (round disk about 5/8" diameter) that lives somewhere on the motherboard. If you've had the machine for a while (3-5 years), it's good to check the battery and swap it out of the voltage is falling. You should have a fresh battery ready before swapping, as most systems have very little capacitance and you could lose your customized BIOS settings during a lengthy swap-out procedure. Check your owners manual for what type of battery backup your system has and how to change it.
If the battery is not a problem, have you or your service engineer tried flashing a new BIOS into the system? Manufacturers may release BIOS updates (sometimes fixes) to the original firmware on occation. That might test whether there is a problem with the physical memory that holds the BIOS. A small possibility exists to brick your system if the memory is bad, but it's looking like the laptop not much use to you in its current state.
Best of luck with debugging the issue.