Error whilst saving Dropbox Category

I am using dropbox with edocman 1.19.3 on Joomla 3 and am getting an error whilst trying to save a Category. The error is a 401 and the message is:

Error
Save failed with the following error: Client error: `POST api.dropboxapi.com/2/files/get_metadata ` resulted in a `401 Unauthorized` response: {"error_summary": "expired_access_token/.", "error": {".tag": "expired_access_token"}}

I find that the Category has been saved despite the error, but if Publishing is set to 'Groups' instead of 'Preset' then that group is not saved either.

Has anyone come across this before, or can shed any light on it?
thanks
Miles

Hi Miles,
This is strange issue, could you please submit ticket and provide your site url with super admin account. I will debug and help you to solve the issue
Thanks
Dam