Armoredman, i am casting with a 5 gang NOE mold also and i agree with what you hypothesize regarding the sprue plate.
what i do (and my bullets drop perfik) is first give the mold a blast of brakleen and dry with a shop towel. I set it on top of the lee pot to heat up while the lead is melting but when i flux i remove it so i don't rely on that to get it up to operating temp.
With the pot set to high for melting, i drop it back to 8 for casting once it's been fluxed. i then fill the cavities by pouring directly into the mold trying not to let the stream touch the sprue plate whatsoever, letting a good heaping pile of lead form on the top of the sprue once it's full. the first castings i will cut the sprue and open the plate but leave the bullets in the closed mold for 5-10 seconds to heat the mold. this is also the time i apply bullplate to the sprue hinge, the top of the blocks, and alignment pins and bushings. i usually repeat this process less the lubing 4-5 times.
i will discard the first 4-5 castings as they usually are not as flawless as i prefer my bullets to be. after that though it's off to the races. i typically pour like it's a race with this mold to keep it hot, and let it cool somewhat after 100-150 bullets cast to re-apply bullplate.