There are times that your default browser is filled with data and temporary files from previously visited websites. With this said, I recommend using a private browser. Doing so helps isolate the issue. You can use the keyboard shortcuts below:
Great to know you're able to create an invoice on another browser, seb2.
Have you tried clearing the browser cache in an All time option? If not, let's try deleting the browser data in that time frame. Just follow the steps in this article: https://support.google.com/chrome/answer/2392709?hl=en.