I have this very same issue (WMA files over a SMB share make Kodi 18 crash; with latest OSMC release from November 2019). I thought that’s a problem with the new music library thingies from Kodi 18 and some of my music files and didn’t bother to investigate – but now I did.
It works without a problem, if you mount the SMB share via /etc/fstab instead of via Kodi, as is explained here: Configuring fstab based Samba share mounts
Apparently, Kodi’s SMB-Code has some serious bugs in it.