I think you are on to something. And now I need to exchange my pre-war tech for a Post War!!!!???Welcome to the forum!
Feather blades most likely work the best because they're sharper. That added sharpness compensates for the lack of blade support the typical EJ/Merkur/Muhle baseplate has. This is something I've said many times. Usually it falls on deaf ears lol.
Give this thread a read: Rigidity in DE Safety Razors
Edwin Jagger DE89 baseplate and blade support points.
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Muhle R41 baseplate and blade support points.
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Both razors share the same basic design in regards to baseplate support of the blade. That lack of support can lead to blade flex, which in turn can lead to what you're experiencing, and worse.
Blade flex cannot happen in a razor such as a post war Gillette Tech because the baseplate fully supports the blade very nearly to the edge. There are few, if any, razors that are smoother and more comfortable than a post war Tech.
Derby Extra is in my top 3 blades. All of my razors are rigid designs but one, the Muhle R41. Guess which razor does not like Derby Extra blades...
A quick search of the forum for the word 'rigid' will return much to read. If you have issues shaving ATG, or any other direction honestly, an increase in rigidity may solve the problem.