all of sudden the power meter to track 1 (which had midi data) spiked and stayed red
I assume you then refer to the level dB meter on the track header, and not the CPU usage indicator in the transport toolbar. If the level meter is red, it means the output on the track is clipping. If the CPU indicator isn’t spiking, then I can’t see why it should not play audio, especially if you muted the clipping track.
What plugins did you have on track1? Was it anything related to the Effectix plugin you inserted on track4?