We have been selling refurbished Polaroid SX-70 cameras in our stores for a few years now with no customer return thanks to the skillful technicians at SweetRoad. Yesterday a customer brought back her SX-70 having problem ejecting film. I did some search and found out the cause/fix to share here.
Symptom: camera works fine, shutter can be released, battery is not dead, SX-70 is able to eject the black card but not the films.
Solution: The pick arm fails to grab and push the film towards the rollers. The black card is thicker and has a small piece of plastic film attached so the pick arm can hold on to it and push, but not for the film. To see the problem clearly, take an empty cartridge, remove the front cover (the side facing the rollers) and insert to the camera, without closing the 'jaw', look inside the film cartridge which is now inside the camera and locate the pick arm on your top left hand corner. The pick arm's 'hook' should be bent downward to level with the first film. Doing so requires some innovation on your side, a long tweezer may work but you need to find a supporting point in order to bend the metal pick arm. I used a small object to create a supporting point and then use a stick to bend the arm. Be careful not to scratch the mirror nearby.
Now after I fixed our customer's camera in my own way, I found this youtube video perfectly explaining how to do it using chopsticks, i.e. you can skip everything I wrote above hahhaa. Hope this helps you too.