We have reinvestigated the collision of gluonic bubbles in an SU(2) model of QCD which was studied by Johnson, Choi, and Kisslinger in the context of the instanton-inspired model of QCD phase transition bubbles with plane-wave approximation. We discuss treacherous points of the instanton-inspired model that cause the violation of causality due to the presence of imaginary gluon fields. By constructing a new slightly modified Lorentzian model where we have three independent real gluon fields, we reanalyzed the process of bubble collisions. Our numerical results show some indication of forming a bubble wall in the colliding region.