They’re all custom kits. Only 3 out of around 20 crash. They all contained a certain set of samples I’d recorded about a year ago. I pointed the samples back to themseleves.. i.e selected Replace Sample but just pointed it to itself.
I then saved the kits and they didn’t cause a crash when the track is removed.
However these kits no longer load in SE 5 so it looks like new kits are not backwards compatible?