In the latest nightly build, the entire workspace except the viewer almost always turns black when resizing. This used to happen to the viewer #1113 but at least in 10.12.4, that issue seems resolved. When adjusting the size of the viewer/combo-viewer, the viewer overflows the right boundary between windows.

It looks like this issue varies dependent on the version of OS. In 10.11.6, while resizing this is the result:

It's probably at least partially due to the lack of OpenGL support on Macs, but it would be really helpful for someone to take this on. While in itself, this is a small thing, the number of Mac specific bugs can create a negative impression. This is a fantastic program and it would be really unfortunate for the increasing bugginess in the Mac build to discourage new users.
Is this still an issue?
It is still an issue in the current nightly build but not in the Morevna release.
This glitch is gone with the latest nightly build!