CSRF token expiry results in unresponsive form.

[CharString]

As an anonymous Submitter
When I let my Session expire
And I click here

And for some reason (time/server things) my CSRF token has become invalid
I do get the first login step

But clicking "Start formulier" does not start the submission, nor gives me feedback.

Analysis:
Backend correctly reponds with a 403 the POST:

{
	"type": "http://127.0.0.1:8000/fouten/PermissionDenied/",
	"code": "permission_denied",
	"title": "You do not have permission to perform this action.",
	"status": 403,
	"detail": "CSRF Failed: CSRF token missing or incorrect.",
	"instance": "urn:uuid:45c5dc8b-8240-4f3f-8553-94de91c5e995"
}

because the POST request contained these headers

Cookie: csrftoken=TrPftlIryvbjBGq63oh3Y7CnT0oVVUeeiPGOOS6hYOfND7lvJzQhfY7L3rMIYBkA; cookie_consent="analytical=2021-07-19T12:11:35.633000+00:00"; openforms_language=en; openforms_sessionid=lm1kgzn4k0sck8u8lof0osahlma4tcb1
X-CSRFToken: ksJHbv1k39EhazO9jROF6ZTbyMlPcTE2ss6yMNI6VsVbD7UuXAJJ2flUTMmFO7zu

and these tokens are not the same.

A refresh of the page resolves the issue.

Probably not related to open-formulieren/open-forms#2291