to walk with a limp
蹁 centers on an uneven, limping gait: walking with difficulty or a hobble.
蹁 combines 足 (foot) with 扁, which likely contributes the sound and relates to the idea of being off-balance or uneven, fitting the limping meaning.
The foot radical 足 beside 扁 suggests a foot that is not working evenly, causing a limp.
For ヘン, imagine a hen limping: hen -> ヘン, and the bird hobbles on one foot.