Water may be entering the framing because the concrete is above the
bearing for the frame.
That's also common these days.
If the bearing for the wood frame is above the level of the ground,
this seems likely.
If that is the case, some water is working its way down off the
concrete step.

A way to flash from the door sill down between the wood frame and
concrete is needed.
That's hareder to deal with at long distance.

TB