we updated our shop from 1.7.x to 18.104.22.168 and face a curios problem: On most of the devices the login form and registration form is working but not on all devices (Exactly, it works on all our devices, but some customers have this problem). After sending the forms the page is reloaded without error message and the action was not successful.
We inserted the hidden field "formkey" but are still having this problem. Any ideas where we can look at?
Our shop is www.begeisternderwahlkampf.de