What yr?
Also are the bulbs glass/incandescent? If yes then change all glass/incandescent bulbs to LEDs.
Glass/incandescent bulbs burn hot & stay extremely hot & will cause the pigtail sockets to open/soften up/open & eventually be burnt brittle & break off in pieces.
When this happens, the high extreme heat from glass/incandescent bulbs makes the plastic pigtails sockets to become loose & therefore not making any contact.
Also check the wires, fuses, relays & switches.
I've changed all the rear brake lights, reverse, blinkers, high stop light, side mirrors front blinkers to LED's. Haven't had any problem at all.
Don't cheap out. Buy Silvania, Philips at your local Autozone, O'Reilly's, advanced auto parts, Pepboys, Napa & Walmart. Yes they are expensive but you're paying for quality & longevity instead of cheap crap.
Hooe this help.