[take77]

Hopefully recording to the SSD works for you.

You mentioned there is no problem when recording yourself.
Try recording with just 2 simultaneous signals next at various buffer settings and see what happens.

However, it may be your setup simply can't handle the processing of 4 simultaneous signals? At least not for the full duration of the performance.

Also, when just recording room noise for long periods there is not much CPU demand.
Sounds like the band is able to record up to a point.
Is the point at which the errors occur at a point in the song where everyone is hammering full-on?

There's much more processing demand when recording fast successive transients coming in all at once from multiple sources.
That would be much more for the processor to handle.
Maybe you're system is only be able to handle a full song performance 1-2 inputs at a time?
I hope that I'm wrong and that you can effectively record 4 inputs with the right configuration.

I can modestly say that I'm only a solo recordist and have always wondered how many signals my desktop can actually record simultaneously.
I just know the faster and longer I strum my guitar the more my CPU works.

I'm sure others on here would be glad to share how many signals they can record at a specific buffer rates/sample settings using a similar system as yours.