exited Sia-UI (Quit from taskbar icon), waited for all processes to end
made a copy of %appdata%/host/storagemanager/storagemanager.json
Checked that all the symlinks were correct
Opened storagemanager.json in Notepad++
Noted that the first entry was 100% correct, but the remaining entries all had the same UID, which also did not correspond to any of the symlinks
converted the missing symlinks from hex to Base64 using
http://tomeko.net/online_tools/hex_to_base64.php?lang=en , and replaced the erroneous entries with the proper UID and Path. Note that I did not change any of the other values, like the Size, SizeRemaining, etc
saved the file and opened Sia-UI. Unlocked Wallet. Everything looks good in the UI, except the SizeRemaining of the folders being inaccurate.
From the terminal (in SIA-UI) I ran host folder remove N:\ and could see (via Resource Monitor) that the files in N:\ were being copied to C:\Sia1\Storage\ - however after this was finished, all the files were still in N: (and a quick check showed that all the files appeared to be in C:\Sia1\Storage\ as well), and the terminal gave the error: Could not remove folder: could not successfully offload specified number of sectors from storage folder - this cannot actually be due to the lack of available space as there is over 930GB available in C:\Sia1\Storage\.
Replicated this with the other 3 erroneous folders, same results (only tried one at a time of course)