un ‧ stuck /ˌʌnˈstʌk◂/ BrE AmE adjective
[ Word Family: adjective : ↑ sticky , ↑ stuck , ↑ unstuck , ↑ non-stick ; noun : ↑ sticker , ↑ stickiness ; verb : ↑ stick ]
come unstuck
a) British English informal if a person, plan, or system comes unstuck, they fail at what they were trying to achieve:
a dangerous area of rock where many climbers come unstuck
b) if something comes unstuck, it becomes separated from the thing that it was stuck to