CMS admin tooltips persisting on screen in Firefox

Silverstripe Version: 4.9.0

When using the admin area in Firefox the tooltips that appear when I hover over certain items have a tendency to persist on the screen. They get ‘stuck’ in place and don’t disappear until I refresh the page. It is an intermittent problem and seems to happen when Silverstripe is performing actions via an ajax call.

Has anyone else noticed this issue?