Sync keeps restarting on each machine + duplicates, triplicates, quadruplicates

I run Insync on a NAS drive, and access it using one of three computers. Except, where initially I could leave the machines running concurrently, now I have to run them separately.

This is because:

  1. InSync loses its marbles and starts creating duplicates, triplicates, quadruplicates, quintuplets of folders. THEN, when it starts doing this, it doesn’t stop. It doesn’t matter how many times I remove them, they reappear.
  2. InSync starts over and syncs everything from scratch. Every single time I turn on my Mac (which is running High Sierra).

I’m seriously at my wits’ end trying to manage ONE folder (on the NAS) which ought to be synchronising ONLY to Google Drive. Instead the program seems to be treating every machine as an individual with different wishes. ALL machines pick up the NAS and ONLY use the folder directly from/to the NAS.

So what gives? Why is Insync doing this? Promises made about duplicates being a thing of the past with the latest upgrade are clearly not being met.

If anyone can suggest any other solution than InSync (given support has NEVER ONCE provided an answer), please do let me know.

thanks
Leticia

Tagging our engineer @marte on this.