What Causes a Hole in Yogurt Loaf Cake?

I've made the orange coriamder yogurt loaf cake twice now. The first time was cooked through but a bit dry. I blame it on using a 9x5 glass pan and not adjusting temp amd/or cook time.

For the 2nd, I got a metal 8.5 x 4.5 pan as suggested in the recipe. This time I baked it for about 40 minutes and the toothpick had very few crumbs (as suggested). However, when cutting through the center today i had a cavity (hole) about the width of a golf ball right in the middle of the cake where the cake was very wet. The rest of the cake was still a bit on the drier side, but the taste is still good.

Two questions:

1. What would cause that cavity? Just needing more baking time?

2. Is the wet portion in the middle safe to eat?

I really like flavor so am trying to get this to work!