Do you mean that the problem is doubled peak? In GC injection this happens if you have back-flash: part of the sample traveled along with stream and gave you first peak, part of the sample was pushed against the stream, and after some delay, returned back and traveled in right direction (second peak).
Possible cause: excessive pressure in the injector line, sudden reaction between the injected material and injector parts, Injection missed the stream and injected sample into wrong area.