Facing "504 Gateway Timeout" Error with Lightsail CDN During Load Testing, No Issues Without CDN

I am encountering a "504 Gateway Timeout" error when load testing my Lightsail instance with the Lightsail CDN enabled. The load test involves only 100 users, so the load isn't substantial. Interestingly, when I perform a similar load test on the Lightsail instance without CDN, no errors occur.

I've reviewed the Lightsail CDN and Lightsail instance configurations, checked the server response time, and monitored resource usage. However, I'm still unable to pinpoint the cause of the timeout issue with the CDN.

Could anyone provide insights into potential reasons for this behavior or suggest additional troubleshooting steps? I've considered factors such as origin server health, CDN cache settings, and gradual load increase, but would appreciate any guidance or experiences shared by the community. Thank you!