When you move your cursor up or down to scroll up/down, if you move your cursor too slowly, then the canvas does not move.

Steps to reproduce:
1-create a document (size, dpi etc does not matter)
2-go to the top left corner (to see a color difference between canvas and UI), press and hold space bar, and using your stylus, move your cursor down (to make the canvas scroll up). Do it SLOWLY, as slowly as you can (I stress that part, if you go fast it will work normally).

optional:
3-repeat step 2, but using your mouse. Krita works as expected with the mouse, the cursor stays in place and the canvas scrolls up or down.

Expected result:
canvas scrolls up or down depending on the distance you've moved the cursor

Actual result:
cursor moves up or down, canvas does not move.


Additional infos:
I made 2 small videos showing both situations (with mouse and tablet):
https://gfycat.com/SpicyRepentantHadrosaurus <- this one is with the mouse. works as you'd expect
https://gfycat.com/FrigidBestGenet <- this one is with the tablet. the cursor moves, not the view. I show it works when moving the pen faster, but not slow.

Another user in the Krita Forums (https://forum.kde.org/viewtopic.php?f=139&t=138771&p=371406#p371406) helped me confirm this bug, he also made small video showing the problem.
http://www.peppercarrot.com/extras/forum/2017-02-03_cursor-spacebar-bug.gif


Linux Mint 17.2 KDE, Wacom Bamboo, Krita 3.1.1
I also reproduced the bug on W7.