Hallo devs,
Here are some of the things that have been a issue/bug with krita in the git build 4.2.0-pre-alpha (git 90cce86)

Panning when focus is zoomed in, ref image gets stuck and does not allow you move in any direction. You have to zoom completely out to be able to pan the page again.
After painting for a time, if the image is rotated, the brush strokes start to lag out really bad.
While painting, if some times my hand touches the wacom's surface, krita will instantly zoom into max.

Assistant Tool
Changing the transparency of guide lines do not retain settings after closing document.

References Image Tool
Reference image disappears or moves from set location after manual/auto saves, but returns when panning the canvas.

UI
In tool bar menu in Plasma, under Windows, the menu vanishes right away and can not access it at all.

System Stats:
Linux gentoo 4.9.76-gentoo-r1 #2 SMP Tue May 8 12:13:35 PDT 2018 x86_64 Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz GenuineIntel GNU/Linux
KDE Plasma Version: 5.13.80 KDE Framewosks Version: 5.48.0