When opening an image which is accessed over kdeconnect's sftp functionality by either double-clicking the file in Dolphin or opening it directly by passing it as a parameter to gwenview on the command line, gwenview will need a long time to close when the X on the window is hit. Long enough to trigger the KDE hung application dialogue.

Surprisingly, if one navigates to said folder from within gwenview and opens an image, gwenview shuts down just fine.

It seems that gwenview might be waiting on some redundant filesystem operation to complete when closing.

Version information:
gwenview:
    $ git log -1 --oneline
    c8edede SVN_SILENT made messages (after extraction)
kdeconnect:
    kdeconnect 0.9.g-1

Reproducible: Always

Steps to Reproduce:
1. Install kdeconnect on an Android phone and on your desktop.
2. Enable "Remote filesystem browser"
3. Browse the remote filesystem of your phone with dolphin
4. From within dolphin, open an image on your phone in gwenview
5. Click on the close window button.

Actual Results:  
gwenview needs around 20 seconds to close the window

Expected Results:  
gwenview closes instantly

This seems to not happen with things mounted over sshfs.

I have not tried reproducing with SFTP mounts other than kdeconnect's.
Both devices are connected to wifi.