Form changed substantially

Good morning all,
Just wondering if anyone encountered that the Form changed substantially. I was on -18 fluctuating between 2 and -20 but after a Saturday ride 110Km and Sunday ride 74km the form changed to -73. I think is some error in calculation but if anyone can think of what can be the cause I would appreciated.
The lowest I had in the red zone -37 and 1 day rest solved the issue.

Many thanks

Hey @adlerlucsi - hard to say without seeing your training data… but it could be due to an error in your HR or power data for one of those rides. Look at your TSS and if it is above say 300… its likely that your data was recorded incorrectly.

Again - I am not familiar with your data so that TSS is only an estimate. I advise comparing the TSS of those 2 rides to similar rides you have done in the past to see how accurate your data was.