Magento 2.4.3 customer needs to login 2 times

I upgraded from 2.3.7 to 2.4.3 and now a customer needs to fill in the login screen 2 times before logging in. The first time there is happening noting (also no errors), the fields email and password are emptied. The second time login succeeds.

I tested in 2.3.7 and there the problem is not present.

What can be the problem, i’m totally lost…