M6030 tractor catches on fire

Hi folks, first post and apologies if in wrong section. Family has been farming over 60 years and have owned many tractors. Downsizing, purchased a M6030 front wheel assist with bucket mainly for hay feeding. At 2040 tractor hrs yesterday the machine self ignited for some reason. Luckily I was home and the fire fighting unit was nearby so was able to put it out. Wiring and fuel line to lift pump wrecked, diesel leaking helped the fire on its way.
My question is whether anyone else has had any experience of this nature?
We have kept the tractor clean of mud and manure by gentle pressure washing. It was used several hours before the fire: I am confident it had cooled down before the event. As I was putting out the fire I noticed the starter motor was turning over but that may have been wires (keyswitch?) touching. I cannot understand why the battery didn't explode as the positive to the starter has it's insulation burned away. Possibly the starter engaged, ran hot and melted the nearby fuel line, but the battery is not taking much charge so maybe not the starter. Any suggestions gratefully received.

Thank you Tooljunkie
Careful inspection at this stage shows the positive lead to starter wends under the hydraulic pump close by the block and more of the same on way to starter.
We will look for arcing damage between lead and components. Will take a few days, but will keep you posted. The other thing is that the tractor was always parked in neutral and the hi-lo lever was engaged with park (emergency) brake on. Reasoning is that even if the hi-lo switch fails and the machine tries to start the tractor cannot move as it is in neutral. Any fault, had it started, then the tractor will move of it's own accord if both hi-lo and gear selector are engaged- sage advice for new tractor owners, perhaps.