Intermittent A/C blowing hot

My A/C will randomly start blowing hot air. Usually, if I wiggle the temp knob, it will go back to cold air, but that solution seems to be becoming less effective. It's taking longer and longer (and more attempts) to respond. Had anyone encountered this?

 

well....had a similar issue with my system locking up on me and I had to turn it off for a bit before I could turn it back on. I believe the lines were clogged. So I evacuated the lines,flushed them, pulled a vacuum and refilled the system. Worked for me that way.

 

It's almost like the blender door flips over to the hot side and I have to remind it to come back to the cold side. I'm wondering, does it default to the hot side if it loses a signal telling it to stay cold?