Button Block Advanced Styling Bug?

Hey,

Ran into a peculiar issue today.

Gutenberg Button Block–
1 – It seems as though my Advanced CSS Style “is-style-squared” has disappeared from the button block styling panel.

2 – As long as I back out of page – the button maintains its proper “is-style-squared” style – even though the style is no longer appearing in Advanced CSS Style window.

3 – But I CANNOT edit or add anything to the page and save it as then it reverts to blank Advance CSS Style window.

4 – If I try to add it back in, then do something else – it takes it back out.

5 – When I do add it back in, it partially styles the button according to my style, but when I add it to a second style, it dumps the first buttons style.

I am utterly confounded. And this happens on both my DEV and LIVE site. So it is a big problem.

Any thoughts are appreciated.