Christian: looking back and your reply in #478, it would appear that you're on Mint, not Ubuntu. It is likely the case that Mint is still shipping the buggy kernel(s).
We can see in #478: "When installing the Kernels provided above, I can again do changes in BIOS and they stay over reboot. However as soon as I revert back to 4.13.0-21 Kernel, the Problem is back."
...Which is exactly what would be expected.
The solution is, after unlocking the flash, do not run a buggy that will relock it.
Christian: looking back and your reply in #478, it would appear that you're on Mint, not Ubuntu. It is likely the case that Mint is still shipping the buggy kernel(s).
We can see in #478: "When installing the Kernels provided above, I can again do changes in BIOS and they stay over reboot. However as soon as I revert back to 4.13.0-21 Kernel, the Problem is back."
...Which is exactly what would be expected.
The solution is, after unlocking the flash, do not run a buggy that will relock it.