Right now we don't give any information about why the client decides to close the session window. If this is the result of an active user choice¹ then this is probably correct. However there are many cases where it was unexpected for the user, and their only recourse in that case is to dig through the log file and try to understand the output there.
¹ Logging out, closing the window, etc.
Some possible cases:
* Network issues (e.g. connection reset)
* Server/remote desktop crash
* Forced disconnect (idle timer, other client, etc.)
When fixing bug 7479, there have been a couple of changes on this theme. These primarily relate to improved SSH error reporting as stated by the bug. Worth covering here, however, is that the changes introduced in the bug above also removed the short session error dialog for a couple of the "active choice" cases mentioned in comment 0:
- When signaling the client to stop (e.g. by pressing CTRL-C)
- On smart card removal if the ThinLinc client is configured to disconnect on smart card removal.