Diagnosis
Liquid is escaping from the sip lid or the main seal. The primary cause is an improperly seated or damaged silicone gasket on the blade assembly.
How to Fix It
Disassemble the blade assembly. Remove the black silicone gasket from under the blades. Clean it and the groove it sits in thoroughly. Any food residue prevents a seal. Reinstall the gasket, ensuring it is perfectly seated in its groove all the way around. When attaching the blade assembly to the cup, hand-tighten firmly until snug.
If That Didn't Work
Check the clear sip lid on the cup lid. Ensure it is clicked fully closed. If the hinge or latch is cracked, the lid itself is defective and the entire cup lid may need replacement.
Heads Up
Do not overfill the cup. The maximum liquid line is well below the rim. Exceeding it creates pressure that forces liquid past the gasket. Also, blend with the sip lid closed, not open.