2004 Genie Z45-25 man lift stalls out after start

Looking for some assistance in diagnosing this issue. I'll be honest, not too sure where to start, but here's some background info.
Has the ford LRG 425. It's EFI. Serial number z452504-23852

Problem:
Starts up and runs ok first thing in AM for about a half hour. Once the engine starts warming up, it stalls out. Then it'll start up for about 10 seconds, then die.
Had 2 techs come out and look at it
1st tech said replace alternator (900$) and if that don't work, replace wiring harness...

2004 Genie Z45-25 man lift stalls out after start

2004 Genie Z45-25 man lift stalls out after start