Maybe there is an issue. The login button after users log out stop to work showing a popup with "Error".
Here is the related code in index.template.php of Ambassador theme:
<li>', sprintf($txt[$context['can_register'] ? 'welcome_guest_register' : 'welcome_guest'], $context['forum_name_html_safe'], $scripturl . '?action=login', 'return reqOverlayDiv(this.href, ' . JavaScriptEscape($txt['login']) . ');', $scripturl . '?action=signup'), '</li>
It seems that
reqOverlayDiv(this.href, ' . JavaScriptEscape($txt['login'])
sometimes doesn't work, as you can see in the network tab of browser dev tools.
Does the same happen to you?