Never thought about a window cleaner being the culprit. That is quite possible. The interior is very clean. )But,All the window coverings were disintegrated, too, which I have replaced.) I removed one button type screw, but it seemed unrelated to the attachment of the wall board. Did discover I can stretch a nice filmy material over the area and anchor it under the edges. Found a beautiful fancy fabric and I will try to work with it that way and fabric glue, if needed.
Mkguitar, we spend time in Az, too, which is why I installed the ford reflectix window