Tracker blocking causes "Failed to fetch"

I have finally discovered why my Wix Velo development crashes: it happens when Tracker Blocking is “On”. This directly, after page load and before the execution of any Velo code, triggers a “Failed to fetch” fatal error.
Solution anyone?

EDIT: only happens on Opera Mobile browser. Opera desktop OK, as all other mobile browsers with tracking blocking set to “on”. So is this a Wix or an Opera issue?