Why does my Polaroid SX-70 stop half-way without ejecting the picture?

Question

I realise this happen when there is insufficient light around.

Answer 1

This usually happens if the film pack is old and the battery in the pack is  low on juice. It may happen when there is low light, because the camera may be trying to charge the flash off the weak battery pack.

Try a fresh pack of film, if you have one.