Succumbed to Old Age

[kaiser]

I believe the roof lining is applied in a process using heat, that makes a glue/foam expand and stick to the substrate.
It deteriorates over time, and the foam turns to "dust". You can get a 3M product (spray glue), but the adhesive is not strong, and repairs are usually not very successful.
I use a few stainless steel pins to hold the lining up. It works fine, and nobody will notice unless you specifically look. If you arrange the pins symmetrically, it looks perfect!