Salesforce Summer 19 issue for outbound messages

[#1]

Issue

After Summer19, When using session id generated by Outbound messages to perform any REST API calls, all endpoints work apart for "Identity" giving Bad_OAuth_Token error.

Resolution

Salesforce is currently deploying fixes for each instance. Please follow the link below to check if the issue has been resolved in your instance. 

https://success.salesforce.com/issues_view?id=a1p3A000001SHNcQAO&title=after-summer-19-session-id-ge...