firmware issues on L322X

I'm encountering a serious issue on an XPS13 (L322X) laptop that seems related to firmware and UEFI.

Context of the problem

Laptop model: L322X
BIOS version: A07

Description of the problem

Most of the times, the laptop doesn't start properly on cold boot. Pressing the power button causes the keyboard backlight to light up but the screen is pitch black and the DELL logo with the boot options doesn't show up. Toggling the caps lock key has no effect on its LED. A short press on the power button causes the laptop to shutdown immediately, and that is all I can do in such situation.

Sometimes, the laptop will function properly: the DELL logo appears, allowing me to enter into setup and boot as expected: I can start Windows 8 or any other installed OS and everything works fine. When an OS runs, I can put the laptop into sleep mode and it will wake back up normally. But if I choose another option (shutdown or restart), the laptop shuts down correctly but the problem will happen when it starts again.

The observed behavior happens 9 times out of 10 after each cold start, randomly. After days of test, it doesn't seem to be affected by:
- any BIOS setting, including UEFI mode/Legacy mode, Secure Boot, Rapid Start, or any other offered option; "Reset to defaults" has no effect,
- battery state and / or whether AC is plugged or not,
- whether external USB devices are plugged or not,
- internal temperature.

Another abnormal behavior is that when properly booted into Windows, I am unable to update BIOS. I downloaded the A09 version for L322X and ensured the downloaded file had the right MD5/SHA hashes. When I run the executable with administrator rights, during the step "Reading current BIOS" the following error occurs like 9 times out of 10: "ERROR 216: Failed to read BIOS from ROM! Status = 1604". When it doesn't occur, the executable shuts down the computer in order to reboot and perform the upgrade, but then again, when the laptop restarts, 9 times out of 10 the DELL logo doesn't appear and the only thing I can do is press the power button to power it off. When, in very rare occasions, the BIOS update utility succeeds in reading the current BIOS and the computer successfully reboots afterwards, it then boots the DOS-mode flash executable as expected, but this one also attempts to read the current BIOS from the ROM, and fails with the same error (and immediately shuts down the computer without allowing to retry the operation).

Context of the problem

The problem seems to have started after I tried to boot from a linux-based USB pendrive in UEFI mode. Before that, I was able to install any linux-based OS on the drive and boot when in Legacy mode without any problem. It is only after having booted a linux-based image when in UEFI mode that the problem started to occur, and hasn't stopped happening since then, no matter what OS I boot on and no matter the BIOS mode I use (UEFI or Legacy mode).

I searched for a solution on the web and found people having encountered similar behavior on laptops from other brands such as HP or Lenovo and Samsung. In all those situations the problem started to occur after booting linux-based OSes with BIOS in UEFI mode. In some cases this has even "bricked" the laptop (see https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557).

Looking for a solution

Since the problem happens before the UEFI/Legacy BIOS has a chance to run, It seems clear to me that the problem is at the firmware level. Since it occurs after a cold start, it must be caused by some BIOS/UEFI-related memory in invalid state. I hopped upgrading the firmware would solve the problem, but since I'm unable to get the flash tool to work I could not verify that.

Could this behavior be related to some known bugs in the computer firmware, particularly its UEFI implementation (I'm using firmware version A07)?

Is there a way to diagnose UEFI-related hardware memory and/or reset it into factory state?

Any help is welcome. Thanks in advance for your answers.