Also here: Event ID 6398 (microsoft.com)

The Execute method of job definition Microsoft.SharePoint.Administration.SPAppStateQueryJobDefinition (ID e7ddc5b6-3089-4108-a8ed-4adc453c7c60) threw an exception. More information is included below.
One or more app state queries have failed.
What can I do to fix this also this is for sharepoint 2013 Foundation or whatever the free version is called

Answer:

Go to the SharePoint Central Administration
Click Monitoring
Then click Review job definitions in the Timer Jobs section
Find the Job that is causing the exception by hovering over the links and checking the GUID in there
Click the job and click Disable