Most of the time CTRL+U shows an empty window
Pressing CTRL+U or selecting View -> Message Source in Evolution 3.26.6 (Gentoo, x86_64) shows an empty window, most of the time. Other times it's a window with the message "Error opening file /: Is a directory". If I insist (10-20 times) it will eventually display the message source. For some reason it reproduces easily with the messages in the 'Sent' folder.
Edited by Ghost User