Sync Error- Illegal start of token

[WightmanAdmin]

When trying to sync data from the field, we are getting the following error message

I've tried to do some research on what could be causing the issue, but it seems like a pretty generic error message that could be any number of things. Hoping to narrow it down and figure out what the problem is. Thanks in advance for the help.  

[Anonymous User]

I have also experienced that this week. The cause was that I included a feature layer that didn´t exist (deleted). I would recommend the following:

- Close collector by swiping it off and restart the app

- Check that all features are correctly shared