If you hear/ feel ANY thunk
If you hear/ feel ANY thunk on accelerating take it in. I took mine into the dealer in August when it first started that, was only on hard acceleration ie pulling out into traffic …at first. They “ran diagnostics” and said it was fine. It continued to worsen/ was happening more often and I took it back in October, said it’s NOT fine. That’s when they found the loose drive chain and extensive damage requiring a new transmission. Just plugging it into a computer doesn’t find mechanical issues. ( mine is a 2019 Ascent).