Works for me FF, Linux. CORS error isn't related to app, it's just Sentry.
Works fine on my Firefox.
On mine also.
It isn't working on my Firefox (94.0.1 in Windows):
From the console I see this each time I try to draw a line:
Unexpected value NaN parsing x attribute. react dom.production.min.js:23:234
Unexpected value NaN parsing y attribute.