Issue with fuel burn reporting

I've been conducting a series of PC-12 validation flights comparing the aircrafts fuel burn with Elevatex, Volanta and Little Nav Map. The aircraft's fuel used indication is my reference. On my lates flightthe results were:

Aircraft: 635 lbs

Little nav Map: 634 lbs

Volanta: 624 lbs

Elevatex:1017 lbs

The Elevatex value is 382 lbs higher than the aircraft's recorded fuel burn.

What makes this interesting is that I've seen this before. On previous flights, Elevatex matched the aircraft almost exactly when i made sure the previous flight had ether been completed or canceled before starting a new one.

This makes me wonder if an active or incomplete flight session is occasionally being carried over into the next flight causing fuel from multiple flights to be accumulated.

Im not concluding this is a software bug yet it may be my workflow issue but the pattern has been consistent enough that i thought it was worth asking. Aside from these occasional anomalies, Elevates has produced excellent agreement with the aircraft's actual fuel burn