I'm using PS 1.6x and I've noticed (another) issues when trying to checkout.
First problem is that when I'm trying to checkout as a guest, I finally get an information that my account was created and I'm redirected to step 1. When I want to proceed, I'm moved from step 1 to 3 (as shown on screenshots).
Another problem is that no customer can register an account:
unable to load form
Error thrown: [object Object]
Text status: Parsererror
However, it doesn't when when selected language is english. I've just tried disabling mobile in my theme but it doesn't work.