Complex sentence: At that time, the breach between McKay and Morris and the rest of the group had became important: a warm-up show in Ireland had caused McKay problems, forcing him to play without all his effects pedals as none of the gear had turned up.
Split into simpler sentences: At that time, the breach between McKay and Morris and the rest of the group had become important. A warm-up show in Ireland had caused problems for McKay, forcing him to play without all his effects pedals, as none of the gear had turned up.