Symbolic links do not display icons in Windows 10.
No problems with them here (screenshot below).
Opus simply asks Windows for the icons and displays whatever comes back (if anything). (Assuming the icons have not been overridden via the Labels system in Opus, but you'd know if you had done that.)
Blank icons are often caused by 3rd party shell extensions which crash when asked to supply an icon by Windows. Some may crash in one process and work OK in another, if they haven't been well tested, for example. Cloud storage and source control shell extensions seem to be the main culprits here, although any with an Icon Handler or Overlay Handler could cause a problem.
With that in mind, please run ShellExView and sort by the Type column. Select all of the Icon Handler and Icon Overlay Handler extensions, then right-click and choose the option to disable them. Reboot the machine, and see if the problem remains.
If the problem is gone, re-enable a few at a time and reboot to narrow it down to a particular extension. Let us know if you find anything, or if you find the problem is still there even with them all disabled and after rebooting.