Hi there,
Thank you for taking the time to share your feedback with us. We sincerely apologize for your experience with the double-walled tumbler.
The hole at the bottom is designed to release pressure that builds up between the two walls of glass as the air expands or contracts with temperature changes. This feature helps prevent the glass from cracking due to pressure imbalances. We recommend not removing the silicone stopper, as doing so may allow water to enter the area between the glass, leading to fogging or reduced insulation.
Please note that our team is in communication with you regarding the replacement tumbler, and we hope this will resolve the issue for you soon. We have also shared your feedback with our manufacturing team to ensure that improvements are made for future products.
If there’s anything else we can assist you with, please don’t hesitate to reach out. Your satisfaction is important to us, and we appreciate your understanding.