If you bungle something, you fail to do it properly, because you make mistakes or are clumsy.
Two prisoners bungled an escape bid after running either side of a lamp-post while handcuffed. [VERB noun]
...the FBI's bungled attempt to end the 51 day siege. [VERB-ed]
Synonyms: mess up, blow [slang], ruin, spoil
bungling adjective Synonyms: incompetent, blundering, awkward, clumsy