Looks to be more tied to the wave diving into the Pac NW, which eventually gets involved with the wave coming out of the SW.
Notice how earlier runs had that wave diving more southward into the West, before eventually trending further NW with less of a dive the past several runs. This in turn has lead the heights being shunted down ahead of the main ejecting trough.
This run seemed to reverse the Pac NW wave issues a bit, but the faster timing of the SW wave ended up still lowering heights.