BOOM plays an extra beat?

[notetoself]

i'm having a really frustrating go with BOOM right now. here's my situation:

BOOM is playing an extra 1 beat of a pattern, so that the 1st beat of my 2nd pattern is played over by the 1st pattern. more specifically, the first pattern has 4 hi toms, all on the down beat. the second pattern just has closed hat on 8th notes. in MIDI, i set the grid to 1 measure, draw 2 bars of pattern 1, and 2 bars of pattern 2.

now, you'd expect to hear 8 hi tom hits, but no, i get 9. wtf.

i've tried going to slip mode to pull back from the first beat of the 3rd measure, but that's asinine. i shouldn't have to do that.

any suggestions?