Bug report: Gutenberg reflow

This bug affects at least Astra Theme version 3.7.7 and 3.7.6. running on WordPress 5.8.3.

When clicking on a paragraph block in the Gutenberg editor, a blue border pops up surrounding the active block. This marker adds some padding on the inside, causing the paragraph width to decrease and the text to reflow.

This is not an issue with Gutenberg itself since it works just fine with the current default themes, e.g., Twenty Twenty-One.