HPLC Analysis related incident

while performing the analysis of Assay by HPLC in standard injection -3 peaks was not elated .analyst identified the problem and stop the sequence and raised the incident .as part of investigation repeated the analysis and also peak was not elated initial performed A and B channel after changed to C And D channel in same system rectified the problem but incident conclusion time need to perform calibration is it required?

Need to call service engineer,
Service engineer find the problem why Initial standard peak is not eluted, If any root cause find for channel A and B, and if any parts changed during service then calibration required otherwise calibration is not necessary.

suhel patel