Posted by Robert Clark on Aug 29, 2020; 4:00pm
URL: https://forum.librecad.org/Selection-of-entities-intermittent-tp5716877p5719503.html

Thanks for the suggestion, but the copy solution did not seem to work for me as that I saw no option to copy into the new drawing.  However, I did find a solution whenever the "Lengthen" object command gave a "No entity found" message.  What worked for me was to:
 1) Close out the drawings and LibreCAD;
 2) Navigate to the working directory and carefully delete the .dfx~ file.  Obviously, I am careful and don't use wildcards as that I don't want to delete the .dfx file.  I assume the "tilde" file is some kind of redo/history file that gets recreated when starting an edit session.

Once the file was gone all the Lengthen functionality worked fine.