Contribution sidebar on Parental Guide editing goes completely dark/black when clicking "Close".

Step by step:

On PC, Firefox browser

Go to a title that has no Parents guide content.
I tested on: https://www.imdb.com/title/tt39281989/?
click "Add content advisory"
click "Be the first to contribute"
Sidebar pops up
select a category
add your details
Does this Parental Guide contain spoilers?
no
Submit
Thank you for your contribution!
Click the blue "Close" button on the bottom
Now the entire sidebar just turns all black ?

I find the contribution approved in my contribution history , the Beta one, not the old one
#260616-193914-426621
https://contribute.imdb.com/contributions/history

But the sidebar is not supposed to turn all black after pressing "Close" ?

See 2 pictures. 

Has happened on multiple titles for days/weeks, don't remember when it first happened.