Bug, feature request, or proposal:
Bug
What is the expected behavior?
When I switch between tabs that both have expansion panels, I want the expansion panels to behave like they would in any other situation.
What is the current behavior?
The panels are sort of opened, and their style is messed up :

What are the steps to reproduce?
Stackblitz
Is there anything else we should know?
Unlike #5269 there's no hidden tab. So I think it isn't a duplicate, hence the new issue.