Just read your post... had not heard of a "mining" BIOS? Checked out the microsite. I see what it does now.
Try resetting your current BIOS to defaults. F10 to save, exit and restart. Upon restart, attempt QFlash again.
Z170XGaming5MIN.F22a should be located in the root of a FAT32 formatted stick. Try formatting it again fresh then copying the file over before you attempt to flash.
Ok, I reformatted my flash drive and redownloaded the mining BIOS, uncompressed it and copied onto my USB stick.
I reloaded the BIOS defaults, and went into QFlash, and I get the same error, this time I got a photo, sorry for the poor quality:

Looking at the photo it seems the mining BIOS is dated the 23rd of June while my current BIOS is dated the 30th June.
Could it be that the BIOS is preventing an older BIOS from being flashed?