So, spoke with Benchmark. They thought the thermal shutdown was from playing the amp for 3 hours or better at that volume level. Said no problems with the 4 0hm speakers. It is stable at all impedance levels. I told them once the amp cooled, we played at the same volume level for another hour with no issue. They said if it happened again let them know and I might need to send it in for a go over as a bit unusual. The album we were playing at the time should have had no impact on the amp's heat.
Second AHB2 on the way.
Second AHB2 on the way.