Green’s Dictionary of Slang

(W.I./UK black teen) a satisfactory situation, peace and quiet; also as v., level the vibes, to calm the atmosphere.

1984		Smiley Culture ‘Cockney Translation’ 🎵 Sweet as a nut... just level vibes.
1995		L. Stavsky et al. A2Z 63/2: level the vibes – v. (Jamaican) to calm down the atmosphere in a music club or elsewhere.