Buy auto buff or auto mp?

I have both on an Evan and notice that sometimes the Auto-HP doesn't kick in. I don't know why, the HP bar flashes that alert but even after subsequent hits by monsters it doesn't refill. I chalked it up to the teleport-into-monster = no activation glitch, but just walking into monsters gives the same effect. So Auto-MP.

if you're in the middle of buffing of some sort, it won't activate, if you have both auto hp and auto mp, and they both have to trigger, the game will only trigger one.

learned this the hard way.