rear brake light socket issue

Hi,my wife's 93 s15 jmmy right rear brake light went out but running lights still works.so i replaced it and still the same.so i thought maybe the tangs that contact the bulb might not be touching so i separated that socket and inspected and looked fine.....alot of grease ugh.after that i took the bulb out and tried to insert 180 degrees and the bulb wont lock in ...of course but the blinker and brake light work no running light..im confused any help would be greatly appreciated and will check back during work.
thank you folks!

any ideas?
thanks

Hi,my wife's 93 s15 jmmy right rear brake light went out but running lights still works.so i replaced it and still the same.so i thought maybe the tangs that contact the bulb might not be touching so i separated that socket and inspected and looked fine.....alot of grease ugh.after that i took the bulb out and tried to insert 180 degrees and the bulb wont lock in ...of course but the blinker and brake light work no running light..im confused any help would be greatly appreciated and will check back during work.
thank you folks!

You need to verify power to the socket when the brakes are applied. Check at the connector to the socket. Many sockets have been replaced for lamp concerns.

ok,i will check that today and post findings
thank you

after checking everything again and found nothing wrong with socket and good ground.so i replaced bulb with another new one and everything is working fine.
thank you for all your help it was appreciated