Hi:
I could not find a previous version on the support page either.
This 3rd party website has a very old BIOS update file for your PC....version 2.05
HP 260 G1 Mini PC drivers (driverscollection.com)
Since there is no revision history or anything available, I don't even know if you can go back that far.
Some BIOS updates inform you that if you update to a certain version, you cannot go back.
Anyway, that is all I could find if you want to give it a try.