stumble
躓 centers on losing one's footing or encountering an obstacle while moving: stumbling, tripping, or faltering.
躓 combines 足 (foot) with 質, which likely contributes the sound and may relate to the idea of substance or obstacle, suggesting a foot encountering something solid and stumbling.
The left side is the foot radical 足, and the right side is 質 (substance, quality). Imagine your foot hitting a solid, high-quality obstacle on the path, causing you to stumble.
For チ, picture a foot tripping over a cheese wheel: cheese -> チ, and the stumble sends the cheese rolling.