Couple thoughts:
1. I once cleaned out the fuel tank on my backhoe. It was near empty so unscrewed the bung in the bottom of it to get residual fuel out. Took a pressure washer and turned it inside the tank spraying as much of the tank as I could while the waste water flushed out the open bung in the bottom. Once done, I took a garden pressure can with some diesel in it. I sprayed the interior of the tank with that to 'wash out' the residual water. Put plug in bottom filled it up, purged it and it's been perfectly fine.
2. Once had a problem where the backhoe would move for bit then die. It was fuel starvation death.... confused me for a couple weeks. Then I looked through the (dirty enhough that you couldn't see through it) glass water seperator.
Turns out it was essentially full of water so the fuel would float on the water and get sucked into the engine. Step on throttle and it dies since there's not that much fuel there. Cleaned out the water seperator, put new filters on and it's been fine since. Because of this though, now I know to look there sooner if I have an issue. (I've also since smashed the old dirty glass bowl and have a new pristine clear one to see through)