If this happens often, try taking a wet toothpick to your shaped loaf half way through the final rise.  Dock or poke it many times so large pockets of trapped air can escape before baking. 

Mini

I make a honey oatmeal Cin Swirl, I found that if the internal temp doesn't hit 190, if falls.  I also found that if I over proofed it I got the same result.  I don't know what your temp should be, but you might try it.

Good Luck

I have tried making cinnamon swirl bread and had similar problems. When I posted on it, I was advised to wet the rectangle of dough with either water or egg white before sprinkling the cinnamon over it. ALso, try to roll firmly and evenly.It did seem to work on my next loaf but I want to see if it consistently works.

but it has given me consistently good results.  It's a recipe for making the cinnamon-swirl filling for a single loaf of bread (sized for a 9x5 inch pan) from the King Arthur Flour Whole Grain Baking book.

Ingredients

1 large egg white

2/3 cup (5 ounces) packed light brown sugar

2 tablespoons (5/8 ounce) unbleached AP flour

1 tablespoon ground cinnamon

1 teaspoon vanilla extract

Mix all ingredients.  Spread over bread dough rolled out to an 8x24 inch rectangle.  Roll dough from the short end, tucking in edges as you go.  Seal the seam.  Place dough in a greased pan, let rise, and bake according to your bread's directions.

From what I see, the egg white and flour help bind the mixture to the dough, preventing separation between the layers, plus the filling develops an almost "cakey" texture of its own, rather than running all over during baking.  Note that there is no fat, either, which could cause the layers to delaminate.

It's been my favorite since finding it.

Paul