as far as changing firmware - is that a bucket of slugs you really want to get into ?

With a delta I think you need to tell it all sorts of things: length of rods and a bunch of stuff.

I have to admit I have never changed any firmware on any of my printers - and, I suspect, as a consequence - never had all the hassle and problems people round here seem to have. probably 60% of our problem threads start with:'All i did was update/change/fiddle-with the firmware....'

Are you using cura as a slicer ?
Would be worth trying something else.
I like simplify3d for the deltas.
But repetier is a good free alternative.
Both give you full usb control over the printers, which makes for better and easier trouble shooting.