System Update failing

I upgraded to 2.3 when it was released, and everything seems to run fine since then.  However, in the past couple of days we've been unable to perform system update tasks.

Inventories run fine, and if I run the troubleshooting tool I can successfully push packages through to the destination server.  However, if I schedule or run-now with any live package, it fails on me.

The essentials server has had a reboot & recent windows update (running Server 2012R2). It's got plenty of space and free resources.

No errors at the time of update task in the Essentials log in eventvwr.

The error is always "File deploy command failed to execute with error message: the deploy operation failed. Unable to copy the file to the remote system"

This error happens on all of our 150 managed servers.

Anyone else had similar?

Cheers,

Ash