Version 20170301 fixed it for me
[As I’m not allowed to post more than one image, I removed the one showing the version]
not only the first, but all pictures and screenshots were uploaded (like these two in my comment)
but older pictures or screenshots in the same directory on my phone didn’t upload…
Nextcloud Server 11.0.2 (stable) on Arch ARM running on Raspberry Pi 2
Nextcloud Android-App from your latest beta link at github
Moto Z Play Android 7.0