When i try to edit a Page with Firefox with the Edit button on a Site i get the Error “Failed to lock the page.” but in Chrome is it still working fine. Also wenn i go with Firefox on that page on the 3 Points menu and open for Example History and click then Edit i came to the WYSIWYG Editor normaly?
There’s no relationship between displaying the history viewer and the edit button. The edit button always edits the page content. And the default editor is the WYSIWYG in-place editor. You’ll have exactly the same under any browser.
Try refreshing your browser cache (or use the FF private browsing mode to verify).
Did you try using Chrome to see if it reproduces there too?
Would be helpful if you could check the network tab in the developer console: when you click on the button, you should see a request performed with a 4xx or 5xx status. It would be helpful to see the answer on this request.