Could someone please please tell me why this is happening. Every single time I bake a loaf of sandwich bread, I have the lift off happening... what am i doing wrong?
Probably underproofing. Using steam is pretty uncommon for sandwich loaves. Can't really tell what sort of pan you're using, but it does look like you got a lot of ovenspring.
1: insufficient steam. Crust forms too quickly and the expanding loaf bursts from the weakest point which is normally the side.
2: a shaping issue.
3. Under proofing so a bit of a runaway oven spring.
4: uneven temperature in your oven.
While I've given a few options it's most most likely #1. Or #1 with a possibility of one or more of the other options adding to the issue.
Probably underproofing. Using steam is pretty uncommon for sandwich loaves. Can't really tell what sort of pan you're using, but it does look like you got a lot of ovenspring.