Dimming the rear parking bulbs when signaling

Hello to everyone. An event that I noticed when I parked my car on the roadside and burnt the quads. When the turn signal light turns on, the rear parking bulb (also the brake) is dimmed to almost extinguish, but this event only happens on the right side bulb, what happened before?

the chassis feels insufficient, the battery may be weakened, a few volts may drop until the electricity is there

Just as our friend Selçuk said, my teacher is buying chassis, probably oxidation etc. Remove the plugs and clean them well and check the socket sockets.