I get the following error, when the case is created with the help of Microsoft Dynamics 365 App for Outlook. When the case is created directly in CRM or in portal everything works fine. The flow triggers when the record is created in Dynamics 365.
I've discovered the issue was down to using characters in the text. Other than using the replace function to parse the text I have no fix. To date I can't find any Microsoft documentation which lists characters that cannot be used in 'Post your own adaptive card as the flow bot to a user' .