Angular 6 Project failed to load resource Error 421 on Iphone Safari 12

Question

after building the angular project with

ng build --prod

all images and files are not loaded in Safari on Iphone 12. In Chrome, Safari Desktop and Firefox it works without problems. The error is:

message: "Http failure response for https://myurl.com/assets/i18n/de.json: 421 OK"

421 Misdirected Request

Build width: Angular CLI: 6.0.8 in Angular: 6.0.5

Thanks!