Trouble Fixing P0455 Code--Need Help!

Hello...I am desperately trying to get my 2004 Chevy Aveo P0455 (Lg evap leak) code fixed. I took my car to a qualified shop with mechanics I know, and they could not find any leaks. They did try swapping out gas caps, but that didn't work. I replaced the evap canister and the purge valve (both located in rear passage well), and that did not work.

I am getting a weird noise and a bump sound from the gas tank area--BUT only when I first start the car, not afterwards, and I believe this started at the same time I got the first check engine light (P0455 code). Can anyone please offer some ideas of what this could be? I am now thinking there is something going on with the lines going from the tank to the evap canister. Please see video here: https://vimeo.com/470277312.