Please see the link with the video in the private section.
The issue is when you are on one flavor and select a different size. Between flavors of the same size, the buttons are correct, as you showed, but when you change the size from 300 to 150, you notice that the selected flavor changes and this is what the issue is about.
I have the same problem. Also after the last update. Now, when switching to a certain color (1 attribute in the variation), the value of the second attribute in the variation also changes.
Also, I noticed that it used to be possible to display options by sorting by attributes (for example, first white, then gray, then black). Now they are displayed in random order in different products.