Fix UEFI bug - is it possible?

[Tomoms]

Hello,
I own an old Samsung laptop (R530-JA04IT) that - surprisingly - has got UEFI v2.0. The big problem is that the laptop came with 3GB of RAM, and from the day I added another GB of RAM by replacing the 1GB stick with a 2GB stick, the laptop refuses to boot any OS (Windows 7, Ubuntu etc) installed in UEFI mode. The new 2GB stick is not faulty and is compatible with the other 2GB stick: if the OS is installed in BIOS mode, all the 4GB of RAM work flawlessly.
So it looks like there is a bug in the UEFI implementation. My question is: is there anything that can be done to fix this issue? I think it's not possible.
Another interesting detail: the PC boots Ubuntu in UEFI mode with all the 4GB of RAM working only if it is installed on the SATA drive but with the /boot partition located on an external drive.

This is weird.

Thank you for your help!