Every time I draw a line on Flash [I do not yet have Animate CC], the line segment or whatever selects on its own.
Here is an example- [a piece of the X has been selected on its own]
Im sorry if the solution is obvious. I only use Flash for short animations for my own entertainment, im not good at all of the technical stuff behind the program.
When in the various drawing tools there is a round icon near the end of the tool palette which is the Object Drawing mode button. Turn that off if you want the lines to be part of the same shape.