I've just tested the steps in bug report #37467, my results:

1. Using whitespace-mode distributed with Emacs 27.0.50, the bug happens.

2. Using whitespace-mode in EmacsWiki, the bug does not happen.

I didn't see in deep to verify exactly what is going on.

Vinicius

PS1: The whitespace.el file distributed with Emacs has a lot of modifications, probably it could start with whitespace.el in EmacsWiki and adding one by one the modifications until reach the bug.

PS2: I saw that all save-match-data was removed from whitespace.el, this could be a starting point, that is, add again save-match-data at original point and check if the bug happens.

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