What is the size of the canvas and what is the zoom value? And are you talking about 200 px on the canvas (as I guess) or 200px of the display (less likely, but possible)?

Created attachment 140244 [details]
Spline handles size

The distance needed is in canvas pixels, regardless of zoom level or canvas size. You have to move the pen entirely across a 200x200 canvas before it registers. 

Problem happens with pen or mouse, and at either 100% or 200% dpi (1080 vs 4k)

Strange behaviors by assistant type:

2-point:
standard, doesn't draw until 200 pixels away from origin

Concentric ellipse:
If the ellipse is a circle with a diameter of 200 pixels, the pen must move exactly 2rad around the circle before registering. At a diameter of 400 pixels, it moves when it reaches 1rad away.

Fisheye:
Same as concentric ellipse

Infinite:
No matter where you start, the next update will be 200 pixels along the line in either direction, starting from the closest point on the line to your origin. It will also draw a line from origin to the infinite ruler before continuing normally, which I think isn't intended.

Parallel:
Standard. Moves 200 pixels either direction along the guideline.

Perspective:
Same as 2-point

Ruler:
The only assistant that seems to work as intended,with no 200-px snapping

Spline:
Very oddly sized spline 'endpoints' on smaller canvases. I feel like this sort of local vs global size issue might be the same root cause of the 200 pixel snapping. See attached image.

Vanishing:
Same as 2 point

Having to move 200 pixels is excessive but this has been seen before.
It may be that you have a large ppi setting for your image.

I'll mark this as a duplicate because it's very related.

*** This bug has been marked as a duplicate of bug 436422 ***