I found, quite by accident what caused the spiking meters and loss of audio. It may or may not work for you, but for me it was a particular midi note. In my case F#2 which was triggering my ride bell. I only realised this because after a restart, the crash would always happen at the exact same point of the song, where I had just programmed a pattern with a ride bell.
I tried changing the cymbal and also unloading the kit piece, but the crash continued to happen, so I loaded the ride cymbal to a different slot and now it’s being triggered by a different midi note. Now it doesn’t crash. If I put an F#2, with or without anything for it to trigger, it will do this crash.
I’m using Cubase 10.5 and BFD 3.4. If you get this kind of crash, try removing each midi note on the bar where it is happening in your midi editor, until you find which midi note is causing the crash. I have no idea how or why this happening, but for me, this is now a solid solution to a problem that shouldn’t really exist, but it works.