By default there are 3 parts to the firmware for the photon - 2 system parts and 1 user part. Each part (obviously) gets loaded at a different address.
There is a make flag that forces the generation of a single monolithic image, see this thread
You might want to try and use the program-dfu target of the makefile(s) - that will ensure that all the relevant pieces match and takes care of the addresses that each gets loaded at.
I run under linux, and did have to make sure dfu-util could run as non-root in order for these make targets to work correctly - your mileage under OSX may vary, but I recommend taking the effort to do that if you can; that way if things get moved around later, you won’t have a problem.