ᐅ Moisture in Exterior Wall Insulation in the Stairwell Area

Hello,
I hope to get some advice regarding my problem.
In 2011, our single-family house was repaired after a fire.
During this process, the exterior facade was insulated with 100 mm Rockwool (4 inches).
In the area of the entrance stairs, the insulation was applied up to the step.
This means there is no splash guard between the stairs and the insulation.
Since I was working away from home at that time, I cannot say whether the Rockwool was installed directly to the step or if Styrodur (extruded polystyrene) was used in that area.
For some time now, a damp edge has developed in this area, showing the first signs of plaster bubbles. It is clear to me that the insulation in this area is saturated with moisture. Over time, mold will definitely form and the plaster will start to fall off.
What steps need to be taken to resolve this problem?
Best regards,
Michael