what edward says is right on the money
this is most likely a battery issue or a faulty connection in the control circuit.
I do need to ask though, does the dash display have any buttons on it? a green and yellow button or possibly a row of buttons across the bottom of the display? You can push one of those buttons while the key is turned off and it will display any fault codes stored in the controller starting with the most recent one first and it can store up to 16 codes for drive and also for hydraulic if it has a scr controller on the pump motor too.
As far as those 4 digit numbers you are seeing, they are drive hours and pump motor hours displaying when the system powers off.
If it is showing those every time the code -07 happens this is telling me the truck is loosing power and turning off while your are driving like the key is being turned off. So in effect you are loosing power to the control wiring in the start circuit somewhere.
Check the battery connector and make sure it is in good condition, no melted contact slots. You can look inside the battery connector where the metal contacts are and if you see any melting on either the positive or negative contact slots it could be loosing power because of this, a bad connection. If you do not find any problem there then it could be some loose connection in the wiring somewhere else.
As edward says though, if you are going to check any of the wiring circuits in the rear panel or under the floor plate make sure you disconnect the battery, jack up the front wheels and discharge the capacitor (if this is the ev100 system) using a metal shunt across the capacitor terminals. Every time you energise the power on the truck the capacitor charges up so just keep this in mind if you are going into the rear of the truck at any time. Touching that capacitor could be a painful experience and can knock you on your butt if not careful. Of course if this truck has the GE SX contollers you will not have to worry about that capacitor, it would be inclosed inside the gray box's out of harms way.