The 8 D-Cell batteries that power the clock's weather mechanism can, on some models, be a little prone to pushing up and against their cover plate. If the batteries are definitely sat in their cradle correctly and making good electrical connection then you don't have to worry. The cause of the slight bulging plates are the tiny tolerances in the hand-welded connections between the backcover and the clock frame.
If the batteries aren't sitting in their cradle quite correctly then you can slightly bend the springs so that the batteries are held in place with more strength:
It’s a simple fix: pull the spring up ever so slightly, as shown in the photo.
The arm holding the spring can also, if needed, be bent slightly at the point marked 'x' in the photo so that the spring remains in an elevated position. This will prevent the batteries being push up rather than across.