Reboot issue on Dell Inspiron 15 3511 after BIOS update

Two months ago, I updated the BIOS on my laptop. Since then, whenever I restart the system, the screen doesn't turn on — the laptop powers on, but there's no display. To get it working, I have to press and hold the Power button to force a shutdown, then turn it back on. Only then does the display work normally.

I noticed that a new BIOS version had been released recently, so I downloaded and installed it. The system prompted a restart, which completed successfully — the display worked during the reboot. However, when I checked the BIOS version afterward, it was still the old one, meaning the update didn’t apply.

I tried several times, but nothing worked. The only way I managed to update the BIOS was by forcing it through the Ctrl + Esc method while connecting the power cable — that updated the BIOS, but it didn't fix the display issue.

I also tried the following:
- Performing a clean update of the graphics driver.
- Booting into a live Linux system from a USB stick (but the screen stays black before the system even loads).
- Clean the RAM sticks and slots using contact cleaner.

Now I want to downgrade the BIOS to the version I was using before the issue started, but I can’t — the BIOS itself blocks the downgrade.

I’ve already tried using the Command Prompt with the BIOS file and the /forceit parameter. The installer runs, "completes," and asks to restart, but after rebooting, the BIOS version remains the same — it doesn't actually downgrade.

Note: I don't believe this is a hardware issue, because when I use the .exe BIOS updater and click restart, the system reboots normally and shows video. If there were a hardware problem, I assume this wouldn't be possible, right?

Can anyone help me? I'm out of ideas at this point.