Meaning of “bug-ru(バグる)”

Bug-ru(バグる) basically means a state in which malfunctions occur due to computer or system troubles. From there, the meaning has extended and is sometimes used metaphorically to describe situations where a person becomes confused or unable to think or act normally.
This is a very common slang term.
Bug(バグ) means bug, and ru(る) is -ru(る) the end of verbs.
So we can say,
Bug-tta(バグった) as the past tense,
Bug-tteru(バグってる) as the present progressive.

Example Conversation

A: The software’s kind of Bug-tteru(バグってる).
B: Hmm, why don’t you try restarting it for now?

A: なんかソフトがバグってるんだけど。
B: えー、とりあえず再起動したら？