CMS admin tooltips persisting on screen in Firefox

<%- if @topic_view.topic.tags.present? %>
<%= t 'js.tagging.tags' %>: <%- @topic_view.topic.tags.each do |t| %> <%= t %> <%- end %>
<% end %>

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?