Teams auto selecting "Missed Calls"

It sounds like Teams is carrying the last filter used between the Activity and Calls tabs instead of keeping them independent.

When you open Activity, Teams defaults the filter to Missed. Because the filters appear to be shared, that Missed selection is then applied when you return to the Calls tab. If you manually change Activity back to All, the filter state resets and Calls stays on All when you switch back.

So it can look like Teams is auto-selecting filters, but it’s likely just persisting the most recent filter across those views.