[Latitude E5550] Keyboard ghosting / rollout problem after BIOS update

Recently I upgraded the BIOS on my Latitude E5550 to the latest recommended version, along with the graphics drivers. It turns out that, while in game, movement keys don't register a lot of the time. I am 100% sure this problem only exists since I upgraded the BIOS.

I looked into it and it seems that the computer prioritizes the keys WASD for concurrent input as per factory settings. However I changed my keyboard from QWERTY to AZERTY a couple months ago, and therefore I used ZQSD instead of WASD. All worked as expected until upgrading the BIOS, and I was able to press ZQSD concurrently without issue. The actual keyboard mapping was handled by Windows, I just had to change keyboard layout after installing the new keyboard.

For some reason upgrading the BIOS sort of re-prioritized WASD, as if my keyboard was standard QWERTY even though it is now AZERTY, and I can register all four of those WASD keys at the same time again but can't use them for movement in game because of the layout. Using ZQSD, pressing multiple keys at the same time in certain configuration simply fails to register in game. Changing keyboard layouts in Windows doesn't change which actual keys can be pressed together.

I don't know if I should roll back to the old BIOS version (but would it fix it?) or if I should remove my keyboard and re-install my old QWERTY keyboard, re-install the BIOS, then remove my old keyboard and re-install the new one again.

By the looks of things, it seems at least some part of the anti-ghosting is handled by software and not the keyboard itself (or it would have been an issue from the moment I installed the new keyboard but never happened until I upgarded the BIOS). Any help on how best to make the anti-ghosting mechanism recognize my keyboard's layout as AZERTY and prioritize ZQSD keys would be very appreciated. Thanks.