Stan and Melisande.
One would need to check that the part holding the battery cover is not damaged or worn.
With the Canon A720 IS camera, both parts were just worn out. But probably after 500 plus times opening and closing.
I doubt that a Canon binocular cover would have such frequent opening...
I had the same problem with my Canon A720 IS compact camera.
After 175,000 individual photos the battery door compartment hinge wore out. I get about 400 shots from 2 Eneloop AAs.
If I put simple clear tape on the camera door it works fine.
But as secondhand A720 ISs cost about £30, I just...