I seem to recall Tod tested a few greased arrows at some point. He also tested the thinner armour used for the appendages and side armours. He also tested glancing arrows coming off the breastplate, along with the helmets above, some shattered and splinters went in thru the eye slits, which would have put a knight out of action (unless maybe he wore safety goggles
) Later helmets had narrower eye slits and snout breathing holes, decreasing their effectiveness at seeing, hearing, and breathing to where knights often raised their face covering when they thought they were out of range . Breastplates developed a diversionary V raised area or rib to redirect splinters. didn't always work. Early pate armour had thick mail around the neck at the front to stop arrows. It also didn't work all the time - plus the force behind even a stopped arrow hitting them there would smart. Later armour changed to articulated neck plates.
In any case, Tod did a few more video on arrows vs. plate, best to watch them all if interested. He even developed an arrow thrower device so he didn't need a 160 lb. draw bowman and could shoot arrows consistently ad infinitum.
Experimental arcaeology at its best. (I love his series on his trebuchet, and he makes more. I liked his rondel dagger vs. mail & plate armour as well, and got him to make me one!)
TWS Playlist <-linky