Any idea what may be causing this? First attachment is how it should look with the topsoil only along the top. Second attachment has the topsoil throughout.
Did you apply this using the Top Strata Layer set to Material nature = Topsoil and 100% unusable for topsoil replacement? If Yes, then the most likely cause of what you are seeing is that the surface you have defined as the base of stripping, is not tying up to your Original Ground surface at its end points. To do that you can add a Tie Slope with Cut Tie set to "Up" (Vertically Up) tying to OG (the surface above it in the strata list. Provided it is tied at the Left and Right ends it should work OK - if the Strip surface base is outside the OG surface this can also cause what you are seeing.
Try adding the Ties to your Strip surface and I think you will find you will have fixed the issue.
If not send me the project and I can take a deeper look for you.
This could also be a Pre 4.11 issue as we addressed some issues like this for your team in CO around this in the 4.1 and 4.11 time frame - so if you are using an earlier version you may also see this in certain scenarios
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