I can add project form frontend and backend successfully and assign user for that project without any trouble. Please check this screenshot through this link – http://postimg.org/image/ikty3wqn1/
Also, you can not add shortcode [cpm_calendar], [cpm_my_task] etc in widget area through Text Widget. When you place this [cpm_calendar], [cpm_my_task] shortcode in a page after then “My Task page”, “Calender page”, “Project page” creates.
Can you please clear your browser cache and test again. I have sent you a screenshot which I have showed you I can assign an user for a project. Did you cheeked the project where I have assign an user?
I have altered a line of code for assign “au” user. Previously auto-complete min-length was 3. I had altered min-length: 2. This alteration will be changed if you update the plugin in future. Better you should create user with min character length 3.
The user “Jam” is an already logged in and created the project. So that “Jam” user is not showing in this project.
For all above the problem we have fixed some code. This is all about programming related. So it is difficult to give you clear knowledge.