First - my correction factor is 0,8398, what seems good (can I set it manually?)
You can set it manually in General settings -> VO2max estimation -> Manual correction factor. And if your prognosis doesn't match your 'real' shape anymore, the correction factor is obviously not good
, Second difference - more important I think - that switch in VO2max calculated from trainings applied to ALL my history. That means all VO2max results in my history dropped by 10-15 (and of course all prognosis too).
By default, the correction factor is automatically calculated by your race results. So if you added/changed/deleted a race result, your correction factor may have changed and caused that difference. The correction factor is always applied for an athlete's complete history. It's not time-dependent, so it's absolutely normal that your complete history dropped by a certain percentage.
The 'goal' should be to find a good correction factor and set that manually to somehow 'fix' it. (And we have on our todo list to send a notification every time the (automatic) correction factor changes, such that the athlete does know what happened.)