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.
Do you have this problem on every CD or just one?

You did not mention what CD player, preamp, or tuner you are using.
By mono, do you mean the same signal in both speakers or just sound from one speaker?
Does the tuner have its own mono switch?
same problem all cd's.by mono i mean sound from just 1 speaker

It sounds like an intermittent connection which once warmed up, makes a good connection. Which, has now apparently failed altogether.

Does the tuner or TT do the same thing? That isolates to preamp or the HKs not the source....If only the CD fails, than that's where I'd start....with the usual swapping cables and such.....