Never see this message again notice flickers on hover

Hello,

I have installed the Pop Up! plugin and customised it to hold a MailChimp subscribe form but the 'Never see this message again' notice (Edited to read 'Please don't show me this again') now flickers rapidly when hovered over directly and is almost impossible to click on because of this. It appears fine when hovering over the popup but as soon as I hover over the actual message it disappears or flickers.

My first thought is that it could be a z-index on hover problem as I have come across similar issues in the past.

I would appreciate any information on a solution on how to fix this?

Thankyou.