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based on your top blade standing straight up in this vid, your blades are too tight. They should swing firmly, but freely. It allows the blades to swing when they hit something they can't easily cut, and divert the force, instead of sending it into your splined shaft area and stripping it. That is likely what is the cause or contributing to your difficulty separating the male/female splines.
Good luck with it

That blade was tied up with a cable. You probably couldn't see that on camera. But yeah...all the blades swing freely.