Stanley Classic Trigger Action 0.35L Thermos No Longer Retains Heat

I purchased the Stanley Classic Trigger Action 0.35L thermos in September 2023, and initially, it performed well, keeping my drinks hot for hours. However, recently, I noticed that the insulation has significantly deteriorated—my drinks cool down within just a few hours, despite the product's claim of maintaining heat for at least six hours.

I have handled the thermos carefully, with no drops or impacts, yet its performance is far below expectations. A premium brand like Stanley should not have such quality issues.

I am requesting a warranty evaluation for a repair, replacement, or refund. I expect prompt action to resolve this issue and restore my confidence in the brand.