I’m having similar problems. In my particular case, the issue with the column items on the presentation page are posts rather than widgets. The title of one post is displayed on two lines, except that the two lines are on top of each other. I glanced through the diffs and couldn’t figure out what change would have this effect, but, oddly, adding the following to style.css temporarily fixed the problem.
.column-header-image {
line-height: 1em;
}
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