Salvete!
I have two instances of firefox open which I've started using the profile manager. My problem is that if I take a screenshot from instance #2, which is not the default instance, the auto-name gotten by Screenshot Captor is a name from the other firefox instance - which means that the autoname has nothing to do with the image I am capturing.
Example
In Firefox #1 (default), I've a tab opened to panda bears.
In Firefox #2, I've a tab opened to chickens.
I push the printscreen button and draw a box over one of the panda bears.
The screenshot gets captured and saved with the name of "screenshot_chicken.png".
I've a related problem due to firefox instances on the browser-tray-switcher application.