If cavers can't fit in there, then why send a small robot in to look for lost cavers? If they can't fit they won't be there.
A robot or drone would be good for checking leads though.
A friend used a camera on a pole to check a small lead one time. Still couldn't tell much because there was nothing
for scale to know how big the passage ahead was. Mostly it just looked like a bunch of rocks. Without something
for scale, it is very difficult to tell how big a passage is. Of course if there were blackness it would work. But if
there were blackness, yelling would probably indicate a big passage. Yelling into a big void usually makes an
impressive echo sound underground.
Sorry, but sometimes logic and common sense really do explain a lot.