At my wits end about the MATE desktop freezes after resume from stanby

[dca00]

When the system resumes from standby, for the next several minutes the desktop is frozen if there are mounted Windows shares on the system. I cannot start new apps from the main menu or from Caja. The apps that are already running remain perfectly alive and well as long as they do not try to interact with the mounted shares. If they do, they also freeze (such as when saving files from LibreOffice etc).

There are the permanent rules for kernel-connections and mount-cifs to the server's port 445, no protocol specified.

When the desktop freezes, I check the events and see nothing being blocked.

But if I disable OpenSnitch, then the desktop un-freezes much sooner than with it enabled, like within 1 min vs 2-3 min.

On this system, OpenSnitch runs on top of firewalld, which also has an allow TCP port 445 rule to the server.

How can I troubleshoot this further?

[dca00]

Today I was playing with CIFS shares and got solid proof that OpenSnitch somehow interferes with them.

user24@localhost:/mnt$ sudo mount WinD 
mount error(115): could not connect to 192.168.27.4Unable to find suitable address.

user24@localhost:/mnt$ sudo systemctl stop firewalld

user24@localhost:/mnt$ sudo mount WinD 
mount error(115): could not connect to 192.168.27.4Unable to find suitable address.

Here I disabled OpenSnitch:

user24@localhost:/mnt$ sudo mount WinD 
user24@localhost:/mnt$ 
user24@localhost:/mnt$ sudo systemctl start firewalld
user24@localhost:/mnt$ 
user24@localhost:/mnt$ sudo umount WinD 
user24@localhost:/mnt$ sudo mount WinD 
user24@localhost:/mnt$ 

While disabled, the shares mount without issues, with or without firewalld running. When enabled, mounting throws the connection errors. Meanwhile, there is nothing in the event log regarding the CIFS protocol. And it is only the mounting! Once mounted, the shares work fine until the machine goes on standby.