2019 Winchcombe Water Ingress to EZS

The other day I started the Mercedes of my 2019 Winchcombe but then couldn't turn the engine off.  Called out Meredes who arrived within the half hour and after a bit of head scratching managed to stop it.  After some further investigation the guy reported that there had been water ingress that had got into the EZS Control Unit and had caused corrosion.  The van was taken into the Mercedes workshop for further investigation / repair.  I received a call from them yesterday stating that water was getting into the unit located under the nearside footwell, down the nearside A Pillar.

Has anybody heard of this problem or know where the water may be getting in.

Many thanks for that.  Had been searching for some time but to no avail, hence the post.