Data from Flight Radar 24 vs another tracking site?

[excel234]

Wondering if anyone is able to shed some light on this. I had hoped to get total flight times for four helicopters. But when I compare the data on Flight Radar 24 and FlightAware, it's wildly different. Why would that would be? I also notice on Flight Radar 24, some flights for the aircraft don't have total flight time and landing time is "unknown." When I click on the excel file showing the detailed flight path, the elevation goes from 200 to 300 and then the data drops off. Does this mean the data is incomplete? Why would that be?

Thanks in advance for your help.