It might be worth doing some random screen shots to see if it's specific to certain apps or webpages as I know some block screen shots so I'm wondering if they may have security settings that might prevent images from being kept? Hope this helps
Unfortunately it isn't. It's happened during web browsing, social media, and even my own phone but it doesn't happen all the time, it only happens every so often and I think it's due to the recent updates as a few people have had the same issue.
Yes, I'm getting the same on my S20 FE. I do a lot of screenshots during gaming and it has always worked flawlessly until recently. I have plenty of space both on device and sdcard (which I've just replaced with a new one). I'm also noting very poor screen capture video quality recently.