I reinstalled the backup app some time ago and it started working this morning so I pointed it at my growing 2015 directory but it only found 113 images. Turns out it doesn’t understand raw DNG files, which is odd because it was able to decode Canon’s proprietary CR2 files. The files it found were DNG files I had converted to demosaiced lossy DNGs.

I pointed the backup app at my output directory instead which is full of Jpeg files.