To reproduce (either do all a or all b steps):
a1. Find a CIFS network share.
a2. Mount it in linux, e.g. I used sudo mount -t cifs -o username=guest,vers=1.0 //IPANDPATH /mnt/netdrive

b1. Have multiple partitions on the same drive for different Ubuntu OSes

3. Make a new project on the drive (if a) or a different partition than the one in which current OS is (if b)
4. Make a new Material
5. Delete the Material

Results: Material does not get deleted and an error message saying "Failed to unload Assets/New Material.mat"

Expected: Material gets deleted.

Reproduced in 2017.3.1f1, 2018.2.0f2