Optiplex 5055 Ryzen BIOS 1.5 Frozen Into (not upgradable) Computer

I would like to upgrade my 1.5.0 BIOS to the latest (in this case 1.15.0).

What I think is the problem, that there was critical bug (issue) in version 1.5.0 and it cannot be upgraded or downgraded anymore.

Side Note: Dell "retracted" version 1.5.0. You cannot downloaded from the old versions.

When one wants to upgrade (or downgrade (downgrade enabled from BIOS)) the 1.5.0 the following erroneous or misleading error message is displayed:

• BIOS Updated blocked due to unsupported downgrade

Like I said, the current 1.5.0 version does not allow itself to be replaced and give this misleading error message.

This issue was discussed in this thread also: BIOS Update blocked due to unsupported downgrade, but no solution was given.

So I am raising again the question, how do you flash again the bios in such a case?