The error happens due to missing original input in 'Emit - Workflow Started TT' in case of timeout after 900s.
The issue can be simply fixed by configuring valid ResultPath e.g. '$.error' in 'Emit - Workflow Started TT' Error handling's catcher.

{
"error": "States.Runtime",
"cause": "An error occurred while executing the state 'Emit - error timeout' (entered at the event id #24). The JSONPath '$.detail.userId' specified for the field 'userId.$' could not be found in the input '{"Error":"States.Timeout","Cause":"","cause":"Customer timedout"}'"
}