Just started to use DraftSight. Does anyone have an issue with the trim command?

I select a cutting edge then press enter then select a line to trim OK so far however next time instead of the little pickbox I get either a window select or crossing select box drawn (this is without selecting any of the command options). This makes it more difficult to select individual lines.

I have watched a tutorial video on the trim command on You Tube but this behaviour didn't seem to occur on the video so I am a bit puzzled. Can anyone offer any suggestions?

Update: Is anyone else getting this problem? I am starting to wonder if there is a setting somewhere which needs to be altered, but I cannot figure this out so far. I have even tried repairing the installation to see if something got corrupted? Maybe a bug?

p.s. the link shown below in the first answer to this post is for the fillet command and doesn't answer my question!