I have downgraded the BIOS to 1.52 again (unfortunately, I do not have 1.53 ... 1.56) and the problem goes away. So it was actually caused by the BIOS update.
I have downgraded the BIOS to 1.52 again (unfortunately, I do not have 1.53 ... 1.56) and the problem goes away. So it was actually caused by the BIOS update.