Sometimes, when I press the space bar to view the answer to a card, the answer fails to appear, however the ‘again, good, easy’ options do appear. So the screen displays the front of the card still, along with the ‘again,good,easy’ options at the bottom, not displaying the answer. Sometimes it just displays a blank white screen with the ‘again, good, easy’ at the bottom. This event occurs erratically and isn’t specific to particular cards. It has happpened ever since I got Anki about 5 years ago- I’ve just started using it again. I have the latest Anki version, and made all these cards today.
This is probably a problem in your card templates. Using things like javascript can cause problems between updates.
You can post the content of your templates and we may be able to help you (See the link above).
If you find the same card sometimes shows content and sometimes doesn’t, while JavaScript is not out of the question, I think it might be a bit more likely to be your video drivers.