Apologies for any inconvenience, we have a few others who have also had trouble with Firefox since the last update.
Some first steps of debugging if you will:
Wordpress, Lay Theme & Laytheme's Addons are all up to date?
Any Custom CSS or JS that may interfere is temporarily removed.
And third-party plugins de-activated to see if this resolves the issue.
If these do not help:
Could you please send your website address, /wp-admin/ username and password and a link to this topic to firstname.lastname@example.org?
Let me know, hope you have a wonderful day and thank you for your patience :)