It was happening in Photo mode with Motion Photos turned on. Until Samsung's next update turning off Motion Photo temporarily works for me. Or use Pro or Live Focus modes.
Ive been having this issue for a few weeks now. I just tried turning off "Motion Photos" and have successfully taken about 20 pictures. Hopefully this solves the problem for now.
I'm having the same issue and it is driving me crazy. I've ended up not getting so many photos because I didn't check the gallery first to make sure it took. My family gets annoyed that I'll stand there taking a bunch of pics and then check to make sure I got one. Super super annoying!!!!
Update -- checked my google photo app and all the photos I thought I hadn't taken are there. Seriously, Samsung needs to fix their gallery app.