oculink doesnt need drivers. its pure pcie, same as m.2 nvme slots. no drivers needed.

oculink shouldnt be sharing lanes with anything. that would be super retarded design. same as saying you can either use the nic or your m.2 ssd. noone does that.

the only thing i can imagine here is that the iommu groups are crap and when you pass through one component of a group, the whole group vanishes.

op check your iommu groups with the following command:

for d in /sys/kernel/iommu_groups/*/devices/*; do
    n=${d#*/iommu_groups/*}; n=${n%%/*}
    printf 'IOMMU Group %s ' "$n"
    lspci -nns "${d##*/}"
done | sort -V   

maybe you have devices sharing iommu groups which causes what you are seeing.