Could not decode input as JSON happening in production starting today

Hi, today we started getting the error below for a small % of our userbase in production (our app has been in production for > 1 year - and this is the first time we've seen this).

It seems to be specific to individual authorized accounts - neither files/list_folder or

/files/list_folder/continue works for those users (they all give the error below) - but when run against other user accounts it's working fine. When a user got the error on /files/list_folder/continue we reset their sync token (so called files/list_folder for the user instead) and it still occured.

Is there a backend issue on the Dropbox end?

Error in call to API function "files/list_folder": request body: could not decode input as JSON