slip, stumble, falter, vacillate
跎 centers on losing one's footing or stability: slipping, stumbling, faltering, or vacillating in movement or resolve.
跎 combines 足 (foot) with 它, which likely contributes the sound. The structure suggests a foot-related action, consistent with slipping or stumbling.
The left side 足 means foot, and the right side 它 looks like a snake or something unstable. Picture a foot stepping on a snake-like shape and slipping.
For タ, imagine a foot slipping on a tar patch: tar -> タ, and the foot stumbles.