Strange GSC fluctuations I can't explain, update, bug ?

Hello everyone,

The GSC stats of my site suddenly change in two 2 days but i can't explain why :
Impressions : increase from 248k to 328k a day
Clicks : remain stable at 10k a day
Average position : from 17 to 24

Is this a bug in the GSC that my impressions increased and my rankings just dropped ? Is a GSC update was put online ? Does anyone experienced that with your sites ?