I’m afraid these things only don’t work because of the Alpha-state/test firmware (3.8A), with which you really can’t expect a stable experience at all, even though they seem to work pretty nicely!
But for me, with 3.7.5A, I’ve always had snapchat 100% working. I had the exact same problem with snapchat though with an earlier Alpha release, but it was fixed with this one. Also, in FB Messenger I can only send text messages, but nothing else, no pictures,video,emoji… nothing. If this is your bug too, I’m afraid this bug is caused by the test fw - and yeah that doesn’t bother me at all either.
I suggest you wait untill tomorrow (Tuesday = test firmware day!), or if you desperately need to send some snaps, try the 3.7.5 firmware! (They made some camera fixes with this one, that’s why I use it and I think it might solve the case for you aswell…)
Also, my Snapchat version is 18.104.22.168