Problem with a D500 decathlon?

I used Xert for 3 weeks and it did work. Today i wasn’t able to do an indoor workout, both on my K3 and on the android app.

Even when It was someone working the smart Trainer became suddenly hard for a few seconds … for.example in a warming up phase at 150w it went up to 320w.

What can i do to check that everything works ? Can it be the trainer that suddenly broke down ?