When in the prefs, the peer listening port does not refresh after Transmission has been running, and after I have checked it once.
Where I live, the port may close over night or over time while Transmission is running. Using the prefs to check if the port is still open does not work so I have to go to http://www.canyouseeme.org/ to check the port. If closed I then Randomize the port and find an open one.
I would be nice if Transmission could keep up to date on one's port status, whether closed or not, or have some other method of checking the ports.