How is the spell of Knock modified on EfU? Mechanics changes page doesn't mention anything, and browsing through old topics didn't result in me getting a definite answer.

Also, haven't tried the spell by itself, only through a ring and a pc-crafted wand. Both instances it doesn't work as it should.

It's unmodified. However by default knock only unlocks things that aren't flagged as plot (meaning, it only works on things you'd be able to bash open anyway).