Yes - files on a mapped drive (share on another server). These icons were placed in a separate fence.
But I have another fence with Icons that reference other files on the same mapped drive (share on a server). They are fine.
I have noticed that icons would disappear following a Windows Update and placing my laptop in hibernate mode. Ususally when I'm at home and not connected to my work network.
Seems to be ok if I shutdown and restart.
Note: Refreshing the desktop does not help.