Exitying Shotcut doesn't kill processes

Please refer to my posts in the How-to/Help area. What I thought was only “a case of the slows” doesn’t seem to be that. The problem is exiting Shotcut doesn’t end two processes called “shotcut”. There are links, in the posts, to screen grabs showing system load and the list of processes.

This happens under Ubuntu 17.10

As I replied in your other topic Linux Mint 17.3 closes the processes without incident. -=Ken=-