I switched roles to a new team, and the first 2 weeks were a trainwreck. It was almost of no predictive quality on how I would do.

Now, there are many reasons why that was the case, and perhaps those underlying issues should be addressed, but from all the role changes I've had, the first two weeks shows how well the group you're going into can onboard, more than it shows how productive the individual will be in the long term.