Perhaps this will help (if I remember it correctly, this started after installing the QuickSubmit plugin): whenever I access the Issues menu option in the backend (either of the submenu options: Future Issues, or Back Issues), the Payments submenu on mouseover looks like so:
and immediately upon switching to any other menu option (for example: Administration, as in the image below), it starts displaying the payment options on mouseover normally - without the need to clean any caches (OJS’s or browser’s):
