Yeah I've had it. Reverb explosion thing, exactly the same as OP describes (presumably the max-out thing sending to aux busses). Really really horrible. Definitely related to automation I agree.
I complained about this last year :
http://duc.avid.com/showthread.php?t=351038
I have a theory that as the floating point architecture has such a massive amount of headroom now it can reproduce these excessively loud thumps that wouldn't have been possible under fixed-point. Whaddya reckon?