Stateless Forms Popups are suddenly being stuck on page after submission.

Stateless Forms Popups are suddenly being stuck on page after submission.

My application that has been working great for 3 years now suddenly this morning has a error. After submitting(Are you sure? message) the popup doesnt go away, it removes the background shading and just sits on the frame. 

Anyone else seeing this? Like I said this code has been stable for a long time, and was used all day yesterday.