obstinate, stupid, uneven, mix
儳 centers on a lack of smoothness or proper order: something uneven, mixed up, or stubbornly wrong. The meanings 'obstinate' and 'stupid' extend from this idea of being off-kilter or not fitting a correct pattern.
儳 combines 亻 (person) with 毚, which likely contributes sound and may relate to unevenness or mixing. The exact historical development is uncertain.
A person 亻 beside the complex 毚 shape, which looks jumbled and uneven. Imagine someone stubbornly mixing things up until everything is out of order.
For サン, picture a person stubbornly mixing sand into an uneven pile: sand -> サン, and the person keeps making it worse.