There are 2 common sized bulb holders, 5/8" and 1/2" (IIRC) be sure yours are the correct size.
Also the OEM 50+ year old holders many times have one of the plastic ears that hold the holder to the cir board broken, might be missing or might be attached but not applying pressure.
Also do not use sand paper or other abrasive on the contacts or cir board. Use a pencil erasure.
check the pins condition many times the pins on the cir board are broken or loose