X_TOKEN_UNKNOWN
Means
design token role does not exist
Typical cause
a typo, or a raw colour that was never a token; a defineTheme() override of a role, radius or font slot that is not in the scale; or — as a Sass @error, so the stylesheet does not compile — a breakpoint rung handed to respond-to / respond-down / respond-between that is not in $breakpoints
Fix
use a role from @ultimat3/ui tokens; for a breakpoint, one of sm md lg xl 2xl — the @error lists them; see Theming