For anyone interested, it was the HF driver. The crossover was fine. We completed the repairs today. The actual repair only took about 20 minutes. Taking apart the proscenium and putting it back together (along with other maintenance tasks) took a few hours longer. It's been a long day.
On the bright side, we did rotate the HF horns on the two center speakers in the exploded array from 60x40 to now 40x60. The downward sound now extends a couple rows farther forward and negates the need for any front fills. It also helps to minimize coverage overlap between cabinets which has caused the whole auditorium to sound like a seamless speaker system when moving from side to side. Of course, it didn't sound bad before, but there was a little noticeable comb filtering in a couple of spots previously.