At 200% text zoom, a button with text like "Check your State Pension age" becomes truncated due to the use of whitespace: nowrap. The content is clipped and everything after the "i" in "pension" is unavailable. This falls foul of WCAG success criterion 1.4.4.
Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality.
Any time the whitespace: nowrap style has any effect on how the button looks, it's an accessibility bug. If you remove whitespace: nowrap, the bug goes away.