Worth checking exhaust back pressure first and having a look at the DPF condition before you go too deep into diagnostics. If the filter is partially blocked, no amount of software work will fix it.
That said, if you're finding these headaches are stacking up, it might be worth considering whether the application suits a diesel unit at all. Short shift cycles with lots of indoor running are exactly the conditions that kill DPF systems. A lot of operations have moved to electric forklifts (https://lindemh.com.au/products/electric-forklifts) just to get out of the regen headache altogether.

maybe th igniter is bad, try to clean the ignition/fire tube.