There was a recent change to how the zoom slider works. It is now nonlinear, more of the slider's vertical space is used at small to medium zoom levels. When zoomed almost all the way out, the only a small part of the slider's vertical space is used.
I'm guessing you are using the zoom slider? It's really not ideal, since the slider is so small. Mouse wheel is best, but I take it you don't have one on your pen. 😉 I fixed a bug with the slider to make it smoother in 2.1.14 and I will make is slightly less sensitive when zoomed out. Also new in 2.1.14 is a Zoom hotkey. You can map this to a tablet button and zoom in and out very easily. The default button is U, so hold that and then move the mouse up/down to zoom.
Also useful is the Pan hotkey, which in 2.1.14 defaults to J and changed slightly so you don't have to hold a mouse button to pan, only the key.