Yes, I think I've figured it out. When driving over bumps Id get some static sound coming out of the speakers. I pulled over and banged the A pillar speaker with my hand and heard the static through the speakers. I then got in behind and disconnected the A pillar speaker (right at the speaker) and left it disconnected. The volume coming out of those speakers was near nothing to begin with, so I figured leaving it unplugged would not make a difference to the experience. I've been driving around all week and no issues with sound (no crackling, no drop outs). I think that either there was something wrong with the wiring to that speaker, or the speaker itself, or the extra load on the amp from using one more speaker, but the issue seems resolved (fingers crossed).
Solution: disconnect the A pillar speaker on the passenger side by removing the trim and squeezing your hand in there and removing the power plug.