Thanks Barb.
The exact error message I get is the one pictured in the original post of this thread. It has no error number as far as I can see.
I deleted the files you suggested, re-downloaded the dock updater and tried again, but no change.
The event log for the attempted update is here:
https://drive.google.com/open?id=1UsQ048tKGyuf5ZC9qra8ZHRhgzdnNICi
Please let me know if there's any more info I can give which can help this get fixed. It's very annoying having a largely useless dock due to what almost certainly a software/update issue.
Regards,
Ben