anyone figure out the problems with Big Sur and A1502s?

[captainmac]

Like the title says:
Big Sur is out a couple of days and i have had about 3 customers hand in their A1502 (from 2013/2014 and 2015) for same issue: update stalled and the Mac ends up displaying only black screen.
After unplugging the I/O-Board the update can be continued, but the I/O Board somehow became fucked after this..
I don't really have so much time to google and figure this out, so was wondering if any of you guys encountered it/figured it out yet.

 

[2informaticos]

Reflash known good BIOS and check if image comes back.

 

[piernov]

Several reports of RIO board being the problem (apart from the usual OS and EFI corruption).

https://www.reddit.com/r/MacOS/comments/jue7n5/_/gceqahn

Also one comment on Apple's forum (at https://discussions.apple.com/thread/252033190 ) that has since be deleted mentioned RIO board too and especially HDMI IC.

There's also an SPI ROM for SD card reader on RIO board apparently that could be related to the problem.
Maybe the update causes the failure, maybe the RIO board had already failed and the update only reveals it.

 

[captainmac]

thanks a lot for the info!
OK. So i guess it's best to just replace the RIO Board then.
Also, if a machine is already in my shop and it needs to be updated by me, do you happen to know (slim chance, i know) if it'll be fine if i run the update without the RIO connected, and reconnect it after succesful upgrade, or will it still be fucked then?