What did you do to downgrade?
If you are running 5.8.5 and install 5.8.4 then the 5.8.5 modules will vanish from disk (same as an upgrade).
If you didn’t e.g. dkms autoinstall for 5.8.4 then you won’t be able to load the kernel modules.
However, it could be a regression in 5.8.5 as I saw my network break earlier when testing linux-lqx, Liquorix kernel 5.8.5 available - now with Clear Linux and MuQSS patches - #3 by jonathon . 5.8.6 has recently been released (https://www.spinics.net/lists/announce-kernel/msg03221.html) so it might help.