Question: What Causes Sliding Top Crust On Bread?
By: Shirley English
Published: February 24, 2010

Sometimes the top crust on my bread seems to come loose and slide to one side while raising or baking. The side it came loose on then has a ridge of bread that has raised out the side.

Answers:
Cookingstyle

You didn't mention what type of bread. Is it sweet bread? sourdough bread? one of the rezones can be. Not enough kneeing or forming /shaping. The type of flour . when using high protein flour it helps develop the "Beard muscles" which helps holding the shape. Will help using water filled with water at bottom of oven for first 10 - 15 Min. of baking, if it is crusty bread like farmer /sourdough bread etc including spraying water every 5 min. . and for sweet bread use it for most of the baking time.
Helen Pitlick

From Twitter: The fan in convection ovens sometime cause this to happen; turn off fan during baking. A banneton for rising the dough helps also.
Curt

Uneven kneading...your right hand is stronger than your left...which would put air in part of the dough and not as much in another.  Yeast was unevenly distributed, too warm or too cold.  Hot spot in oven or as Helen said...convection fan may be an issue.