I have had issues when using Remote Desktop Manager Free (RDM) for MAC OSX.
Firstly ensure that you have iterm2 selected as the terminal
Next you want to be sure you are using the Legacy Engine set to NO under
Preferences > Types > Terminal:
I filed a bug with Devolutions and here is the reference link: https://forum.devolutions.net/topics/35957/doubleclick-select-in-terminal