What causes gaps/holes in homemade bread?
It's typically a problem with large pockets of air in the dough before you bake it.

For the cinnamon swirl bread, try to make sure that you're not getting air trapped when rolling it.  

For other loaves, you want to make sure to punch it down well after the first rise, and make sure you aren't trapping air in it if you're doing a stretch and fold when shaping it.