I am running Linux Mint MATE 19 as guest on Linux Mint Xfce 18.3. I have been tinkering with the VM's fstab, specifically to mount an ext4 partition named BACKROOM, which exists on a separate internal HDD. The host's standard user account (i.e., ray) owns BACKROOM.

I boot the VM and take the following steps in the VM. First, as ray, I open Caja. It says BACKROOM contains zero items. I hit F5. Caja is sure: zero items. Then I go to sudo caja. It says BACKROOM contains 15 items. I go back to ray's Caja session and hit F5. Now it agrees: the truth of the matter is, BACKROOM actually does contain 15 items.

It appears that root's access of BACKROOM, in the VM, makes the standard user aware of BACKROOM's actual contents. The explanation may have to do with the fact that, while ray owns BACKROOM in the host, root still owns BACKROOM in the guest. Permissions in the guest are not greyed out in root's Caja > right-click > Properties > Permissions tab; but when I try to change them, I get "The owner could not be changed." In the guest, sudo chown ray:ray /BACKROOM produces "chown: changing ownership of '/BACKROOM': Permission denied."

My questions are, (1) am I correctly interpreting the reason for Caja's change of mind, regarding the number of items in BACKROOM, and (2-3) (how) should I change ownership of BACKROOM to the standard user in the guest?