Configurator 2 - Operation Not Permitted

When I try to send apps to iPads AC2 downloads the apps OK but then comes up with an error message

"An unexpected error has occurred with these 10 iPads. The operation couldn't be completed. Operation not permitted [NSPOSIXErrorDomain - 0x1 (1)]"

I called Apple support and the guy told me that "this is a known fault and there is no workaround. Please wait for an update."

Meanwhile I've been waiting for 7 weeks and have 20 iPads out of action.

Has anyone seen this fault? Any suggestions for what might fix it?