We are planning bathroom renno in FL vacation house. The single window in that room now is in the original corner shower where the tile is failing from water intrusion. The shower will be gutten back to studs--this is concrete blook exterior house and this window is on exterior wall.
It has been replaced and is not original.

I have suspicion that part of the water intrusion might have come from the window being installed into the original shower rather than replacing the window AND redoing the shower to ensure proper waterproofing occurred.
The failing tiles are on wall and very close to the window ledge--although it is easy to see that the rest of the tiles aren't in great shape--the window wall is one most weak, and it is parallel to shower head an opposite the door.

Can they ensure the window is properly installed w/o taking it out or should we require in the contract that the window be removed and reinstalled to ensure that it is waterproof? Or wait to see?
Just trying not to have change orders which for this contractor seem $$.

This wall will have cabinetry under the window and will be sheetrocked/painted. We are taking out the original acrylic tub and putting in large wall to wall shower on opposite wall.