Hmm, odd that I have this Medion Gf3 Ti200 - MS-8839 card out for testing right now. It looks like a very close relative of the MS-8850. The ram is a bit rubbish on this medion card with 5ns / 200MHz (400MHz DDR) chips so perhaps not a complete match.

I'll get a backup of its BIOS file when I test it later.

But checking this archive: https://archive.org/details/whitebunny-video-bios-roms
The attached file is the MS-8850 103T rom from that archive that looks like it was backed up from a running card possibly:

That was the first file I opened out of the set of GF3 Ti200 ROM files.

Hopefully it should work, what settings are you using with NVFlash? Perhaps there's some part of the ROM that's not reflashed normally and that needs reflashing with the right options to make the card work again?

Wow, thank you, this is just cool! I will try it as soon as possible!

So I tried to flash my card with the attached bios file and again Win98 do not recognize the card. Options I used for the nvflash were: nvflash i=0 -5 -6 bios.rom.

Do you know if the video card works as a secondary card and can display through it? See this video for what I mean - you set the BIOS to boot from PCI VGA first and use the AGP as a secondary display: https://youtu.be/H2rIfqd_-rg?t=268

Here's the backup from my MS-8838 card which may have different clocks or be set up for different RAM, but the main card layout is essentially the same.

I would have to try again with that firmware because I already used the bios from ASUS again. The problem could also be the size of the .rom file with version 103. The one from the archive is 48kb while all the others, including the one from your MS-8838, are only 47kb in size.