I have been having severe problems with my data (speed and power) from trainer rides recently. I would just blame my Elite Tuo, but am not sure it can explain all the abnormalities in the data.
Basically, I get inconsistent powers for close to identical speed and resistance (eg after a lap change there is sometimes a sudden change by more than a factor of 2). Some of the powers are impossible, however much I flatter myself (eg 550W for an hour) and while most of the speed data looks spot on, something is very weird about it.
Eg today, I spent most of the session seeing speeds just below and above 40 km/h (which I believe was dead right) but the session has an average speed of 90.3 km/h. Inconsistently, the max is reported as being lower than this.
Doubtless there is someone here who would be able to glean some useful information from the fit file, so here it is: