Those are both mpu controlled 555 twist style bulbs mounted on Printed circuit lamp boards. Sometimes the small metal "ears" don't make good contact on the solder pads when the socket is installed. Try putting a little pressure on the lamp socket to see if it is intermittent. You can also carefully (not too much force) pull the ears a little so they contact the solder pads better. Sometimes the sockets break inside and need to be replaced. Sometimes you can bend the leads on the bulbs outward a small so they fit tighter within the lamp socket. Make sure the wires are not broken or loose at the connectors. It could be cracked or cold solder on the header pins on the lamp board which can be reflowed with fresh solder.