harman kardon hk775 amps

i recently started using a new to me pair of Harman Kardon hk 775 mono bloc amps and ADS m15 speakers.I am now experiencing an unusual problem.When i fire the system up playing a cd I get a momentary skip or dead spot towards the end of the 1st track and intermittently on the 2nd track,by the time the cd is finished i can go back and replay the entire cd this time no dead spots plays perfectly.secondly i now cannot get a stereo signal when using fm tuner only mono,perfect stereo in any other mode.any suggestions.