It is common to have slight tears to D20 dice mold due to the small opening vs the actual size of the dice.
In order to prevent tears, you can use mold releasing agent, soak in warm or soapy water before demolding and push from the bottom of the mold up.
Please refer to this guide to better care for your molds:
https://sophieandtoffee.com/silicone-mold-care-guide
Replacement or refund requests will not be acceptable in this case.