If the base css has something like the following:
box-sizing: border-box;
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
This will break the layout of the kendo controls.
Adding the following override will fix it:
[class^="k-"], [class*="k-"] {
box-sizing: content-box;
-webkit-box-sizing: content-box;
-moz-box-sizing: content-box;
}
This catches all elements that have classes with "k-" at the start and overrides the box-sizing back to default.
Consider adding this to the kendo css (either the wildcard version or to each k-* class).