I just recently had a freakish incident due to low battery. It was a do not start/or did start but did not run long, like a block or two.
Having once run a completely electric free, battery dead,dead,dead, diesel Mercedes Benz 300SD from New Orleans to Chicago - I was in the mindset that a running diesel needs no electricity.
It took awhile to get too as I thought I had pump problems etc...... Anyways, just for giggles check your battery.
My VW with low battery gave NO indication that the battery was low, all cabin electrics seemed fine and I did not notice the starter RPM change that must have been there. My issues in my TDI occurred with a 40 to 70% charge level measured.