Never have more than one powder container open on the bench at a time.
This one has come up a bunch of times. Nother vote.
I once many years ago added some 3031 to a powder hopper with an inch of 2400 in it and proceeded to load a couple dozen rounds of .30-30. Couldn't figure out why they were so loud and hitting so high on the target!
Marlin 336 action is mighty.
