Katakana 4.5k Deck Audio bug/error

I started using the Katakana 4.5k deck and I am noticing a visual bug. At first I thought that the cards just didn’t have audio. The spot that is supposed to have the play sign (like in the 10K deck) is just blank on my screen. However, if I click on the blank spot it plays the audio for the word.

Not sure why the play button is not showing, but figured I’d mention it. I am using Firefox, but have never had that issue with the 10K deck.