@Saul_Hansell It appears Insync has encountered a bug. A few questions:
At any point, did Insync ask you to login to your account again, and did you do so?
At the first step, am I right to say that you setup the account, and then selectively synced only some of your Drive files? And these were downloaded without any problems?
Finally, could you send an email to support@insynchq.com with your log files so we can take a closer look? How to find the log files
Thank you and we hope to resolve your issue soon.