Transparency Issue
Product: The Sims 4
Platform:Mac
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.63.136.1210
What expansions, game packs, and stuff packs do you have installed? Get To Work, Get Together, City Living, Cats and Dogs, Seasons, Parenthood, Jungle Adventure, Perfect Patio Stuff, Movie Hangout Stuff, Backyard Stuff, Vintage Glamour Stuff, Laundry Day Stuff
Steps: How can we find the bug ourselves? Place the Mahoney Geometric Banister on a staircase.
What happens when the bug occurs? The transparency is broken around the metal parts of the banister. 
What do you expect to see? The banister should be properly transparent around the metal parts of the banister.
Have you installed any customization with the game, e.g. Custom Content or Mods? Never used.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 
As you can see in the image below, there are black boxes around the metal parts of the banister, thus ruining its transparency.