i went to shop last night for supplies and got pulled, breatherlised the lot

Anyway the reason for him to pull me he said was that when i braked my rear passenger side light went out and no brake light on that side

he gave me a 2 week thing to get it fixed and to take the van to a mot station to get stamped up

i've had a look this morning as i was thinking maybe a dodgy earth or summat.... well i checked and cleaned the earth wire to no avail, ive also re drilled and put the earth wire in a different place and still the same is happening. when theres no lights on the brake light isnt quite as bright as the other one, and when i put the lights on its still going out..

any help appreciated cheers hank