-Is there a bur on the sole of the plane that is scoring a light groove and this leads to the shaving splitting? If so, why on all of your planes?
-Is there a nick in the blade edge? A nick would most likely leave a raised defect in the planed surface
-Are you not getting the bur off all the way? Even if you think you’ve removed the bur and don’t feel one after stropping, do a small amount of work with the blade, take it out of the plane, and feel for a bur again. You may find one, indicating that you are making a heavy bur during sharpening and not really getting it off. I had that problem for quite a while!
The mystery is why this would happen to all of your planes and always be in the middle. Is there something about how you store the planes or handle them? A shared history of hitting a corner of the vise? Very puzzling.