Is the rubber thing in the reservoir suppose to be under the brake fluid?

What is your question?

Brake & battery light turns on & off while driving. Checked battery fluid and noticed the rubber thing on top of the fluid. It wasn't there before I had all 4 brakes worked on.

What makes this problem better or worse?

The lights come on & go off randomly while driving.

How long has your 2001 Mitsubishi Diamante had this problem?

Last 6 times it was driven