Running Racket 8.4 [cs], the following example program:

#lang racket
(require plot)
(parameterize
    ([plot-font-size 12]
     [plot-font-family 'swiss])
  (plot (vector-field
    (λ (x y) (vector (+ x y) (- x y)))
    -2 2 -2 2)
   #:x-label "abcdefghijklmnñopqrstuvwxyz"
   #:y-label "abcdefghijklmnñopqrstuvwxyz"))

Results in rendering the y-label, with some letters (h, n, ñ, u) incomplete.
Notice that there is no problem in the x-label letters. In other font sizes this problem may not happen.
Something similar happens with the 'decorative font.

Thank you in advance for your support, and congratulations for the great work.
Best regards.