Domain Transfer to Cloudflare = Internal server error (code: 10000)

I want to transfer just one domain to test Cloudflare as registrar but unfortunately, on the " Confirm contact information" submission I get:

Note that I added the console with the sole error I found (a few warnings though).
I’m using FF 64.0.2 on Win10Pro, with NoScript activated (but only Goole Analytics and NewRelic are blocked).

I didn’t find any Support category about domain registration :frowning:

It worked on Chrome.

Side note: Please allow option to switch currency (you and/or PayPal before submitting payment).
Currently I’m charged $8.03 PLUS bank fees for currency conversion.
PayPal’s conversion fee is much lower than my bank currency conversion fees.