undependably

/ˌʌndɪˈpɛndəbli/
adverb
  1. In a way that is not reliable or trustworthy; inconsistently.
    • The bus runs undependably, sometimes arriving twenty minutes late.
    • The old computer undependably crashes whenever you try to save your work.
    • He undependably changes his plans at the last minute, leaving others in a bind.