Pen only making horizontal or vertical lines, undo doesn't work.

[airmax]

I was using photoshop, clicked the pen off to the side and in a split second my worst photoshop nightmare happens. My pen now only draws straight horizontal or vertical lines, and the undo doesn't work. Really cool feature, but not what I need right now. What is happening, and how can I prevent this from ever happening again forever? Quitting doesn't work, recalibrating, nothing.

[c.pfaffenbichler]

What have you done for trouble-shooting so far? 

Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:

https://helpx.adobe.com/photoshop/kb/basic-trouble-shooting-steps.html

[JJMack]

Can to post a screen captire so we can see what you see????