For starters, replace the light bulbs. The two halves of a broken bulb filament can sometimes be close enough to arc, which sends the draw way up to fuse killing level. Next, check the brake light switch; clean overall and then with contact cleaner. Be confident that it's closing and opening the circuit properly. Let us know what happens next. Do not employ a hammer for any of these procedures, no matter what a Hoon hanging around here says!