Using k-button with the "min" version of common.css shows buttons with display: inline-flex.
This does not happen with the non-'min' version in the 2017.1.223 src download , "kendo.common.css" file. (2017.3.913 src download doesn't appear to be available yet.)
Don't have time to investigate, just thought I'd mention it to see what others are seeing. The inline-flex attribute seems to make buttons wrap strangely onto new lines.
This is inside a kendoWindow, may not happen in normal circumstances.
The file size difference is very small, 259kb vs 210kb approx., so I'm just using the non-minified version.