Jurgen,
I would take this back to MMC. My 94 4/4 had the same screen and never rusted even thogh 10 plus years old.
Not the same for the mild steel body.
You could also change the top rail for a Simmonds version.

Sad to hear though.
John

JohnV6
2022 CX Plus Four
2025 MG ZS EV aka Trigger