In the "green banner" (from 2017) the radius of the einmalig/monatlich/jährlich buttons are not consistent:

"einmalig" has a bottom-left corner radius of 0, while the opposite "jährlich" has top and bottom rounded corners on the right side.

Suggestion:

Make "einmalig" bottom-left corner rounded, too. (same radius as other buttons)

Background: Seems that the "outer" corners of each button group are rounded. Since the frequency buttons are only on one line, their left and rightmost buttons need to have rounded corners top and bottom.