When I try to update a unit from the admin dashboard I get a 'Are you sure you want to leave this page' message. If I leave the page, changes are lost. If I stay on the page I have no way to save my work except to Update again and the same thing happens. See screenshot from https://www.lstonline.ac.uk/lifelong/wp-admin/post.php?post=2300&action=edit
Note that this confimation box appears form wordpress while it is makinf some ajax call and it is not completed yet and when user clicks on the update button meanwhile it shows this popup.
Seems like this is causing due to https error .
Please try disabling the https from your site .
I have the same problem. Even if I wait, I still cannot update (example http://marvinoxenham.org/wp-admin/post.php?post=2113&action=edit). Can you tell me how to disable the https from the site?
Please send reply by email - box ticked now.
Well that could only be appear in case when some ajax call is yet to be processed by the server and meanwhile you click on update button .
this usually appears when you have many media embedded in the content of the page and wordpress is yet processing it .It can also appear in case of js errors .Please check if there are any js errors in your site :
https://codex.wordpress.org/Using_Your_Browser_to_Diagnose_JavaScript_Errors
Share screenshot if there is any and also try deactivating third party plugins for this .