Content has been working swimmingly until we now we can't upload any files. Any ideas from the group or Salesforce?

Error: Your organization has exceeded the request limit for the service you are trying to access.

We're unable to upload files or create ContentVersions via APEX in our sandbox.  The above message is what's presented when a user tries to upload a file. Below is what's logged when code tries to create a single ContentVersion. 

APEX Error: System.UnexpectedException: ContentPublication Limit exceeded.

We are far from any of the limits on content as listed here: 

https://developer.salesforce.com/docs/atlas.en-us.206.0.salesforce_app_limits_cheatsheet.meta/salesforce_app_limits_cheatsheet/salesforce_app_limits_features.htm 

We are only using 41% of our file storage allocation in this sandbox.

Is there a way to see our limit and usage of the "ContentPublication Limit"? The Setup>Overview doesn't seem to list it, nor does the System Limits APEX class. ( https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_limits.htm)