There could be two reasons for this:

1. Smoothing is set to 100% and so all strokes will be auto-straightened. Smoothing is controlled by one of the 3 buttons in the middle ring of the tool wheel (the icon is a squiggly line). Move the slider to 0% to have responsive strokes again. Watch this section of our Getting Started video to learn more.

2. Snap or Align to Grid enabled. In this case, everything you draw will line up with a grid. To turn this off, expand the Precision menu (the 9 dot button) and tap the Snap option to toggle it off. Take a look at this video to learn more about Snap to Grid.