Turned out to be a driver issue. The default Microsoft XHCI driver was not behaving properly with this card. Found an ASMedia driver online that fixed the issue.
Hello Proxmox Forum, I originally posted this on the Proxmox subreddit but am re-posting here as well for visibility. Original post is here: https://www.reddit.com/r/Proxmox/comments/t0o75j/usb_32_asm3142_passthrough_windows_10_requires/?utm_source=share&utm_medium=web2x&context=3
I just bought...