Apport hang opening bug on Gimp 2.8.22 installed in snapd

On Ubuntu 17.10 I installed gimp using Ubuntu Software. Gimp (2.8.22 according help-about) has been installed in snapd with many error messages (failed to read from snapd, failed to write to snapd...) but it works.
from apt seems not installed
corrado@corrado-aa-0919-p9:~$ apt policy gimp
gimp:
  Installed: (none)
  Candidate: 2.8.20-1
  Version table:
     2.8.20-1 500
        500 http://archive.ubuntu.com/ubuntu artful/universe amd64 Packages
corrado@corrado-aa-0919-p9:~$
gimp works fine on pictures existing on local drive, but is unable to access pictures residing on same harddisk different partition with a message 'Could not open... Permission denied. The same pictures are accessed smoothly by Image Viewer or Shotwell.
With the message 'Could not open...' on the screen I attempted to open a bug with ubuntu-bug -w or ubuntu-bug id# but apport seems hang collecting problem information with a message: The crashed program seems to use third-part or local libraries.
Gimp 2.8.20 installed via apt in Ubuntu 17.10 in a different partition of same disk does not have this problem.
I have various screeshot about this problem but I don't know how include them.