Odd laptop behavior - disk write errors

I often take my MBP out to track simple projects, ADAT into MOTU Traveller with FW to MacBook Pro 2010. I’ve always been using Cubase, recording up to the 8 channels available to me through the ADAT. It’s an older MBP, so I don’t push things hard, knowing it has limitations.

Recently, the studios Cubase dongle went to my writing partner for some preprod on new project and I’ve had to use Nuendo on the system on a choir recording tonight.

For some reason, I can’t record more than 2 channels before the drive hits 100% activity and stops recording… I’m not sure what setting I could be missing - I’ve tried turning multithreading on/off, ASIO guard, changed buffer sizers all the way from 128 through to 1024

Anyone have some ideas to suggest?