Final answer:
The best defect report summary is "Typical funds-transfer transaction results in termination of customer session, with a delay in availability when attempting to reconnect" as it clearly states the issue and its impact on availability for customers.
Step-by-step explanation:
A good summary for a defect report in the described scenario would be option D: "Typical funds-transfer transaction results in termination of customer session, with a delay in availability when attempting to reconnect." This summary effectively captures the critical issue of the failure, including the impact on stakeholders, which is crucial for prioritizing the defect resolution.
It clearly communicates the problem that occurs during a common user transaction and the consequential issue affecting system availability.
Such a summary enables developers and product managers to understand the severity of the problem and the negative experience it causes for the customers, thereby highlighting the need for a swift response to address the problem.