I recently noticed paint bubbles where the roof meets the windshield.

When I noticed paint bubbles at other places, the bubbles also showed brown crack lines.

This time however, the bubbles are very smooth and healthy shiny white. I am not sure whether they were there since long time ago, or they occurred recently.

There are also two tiny bubbles under the rubber, but they do not show any brown crack lines (the black stuff you see on the picture is rubber).

Do you think rust is growing under these bubbles? Or can this be just result of poor paint work done by a body shop to which the previous owner went?

The car is 1992 300D arctic white.

Attached Thumbnails

       

__________________
1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.