Ok, so I installed 17.0.2 and the latest API Script versions and the following error manifested:
"Starting webworker script..."
"Loading 1017 translation strings to worker..."
"5eShapedScript 1520360533258 INFO : -=> ShapedScript v13.0.0 <=-"
"5eShapedScript 1520360534875 INFO : Detected sheet version as : 17.0.2"
"Sheet Worker ERROR: Unable to find valid character with ID -L6wY9o7cGpMruj8KvS0"
When I restarted it later the error message had changed ID:
"Sheet Worker ERROR: Unable to find valid character with ID -L6wkijlJ3v6lkGa0Y4t"
Working on figuring out what version of SKT I have, while I wait for them to tell me how to find out, I did the following experiments:
(1) Open an NPC that I have not opened before
The "Processing convertFromOGL" message with smoothly rotating circles - no change after a minute. No messages on console.
(2) Open an NPC that I have opened before the problems started
All good, no console messages.
At this point I realised that the link to the compendium isn't showing (it was determined by character sheet) so I forced it to be visible in the settings.
(3) Copied in an NPC from the compendium that was not in the module
The "Processing convertFromOGL" message with smoothly rotating circles - no change after a minute. No messages on console.
Will let you know as soon as I confirm the version of the module and repeat these tests.
*****
As an FYI - I have added a lot of custom content to the module (maps, tokens, monsters and handouts only) so would rather not have to start afresh if I can help it, but if that's the only option then so be it :-)