repetitive clicking noises after a couple of hours of use

[Coffee_fan]

Hello, I am new to this forum as I bought a Devialet 200 a couple of weeks ago. I am having a problem which I do not think I found an exact replica in this forum, but something along the lines. 


I have been playing my D200 with several speakers. One set of speakers the Bryston Model T signature loudspeakers, which are 4 ohms. At some point, the speaker started emitting cracking noises from the twitter. Turned off the amp and back on and the problem was gone. Then another time, I hooked up a pair of KEF LS50, after a while a ticking noise, with possibly a frequency of some 40 to 50hz started coming through the speakers, not too loud to surpass the music but clearly noticeable. I turned the amp off and then back on and things got well. Nevertheless, after a while, the tweeter of the LS50 started sounding harsh. I turned off the D200 for some 20 minutes and then back on and the symptoms seem to have disappeared. My question then is what is this noise?

BTW: I am on the latest firmware.

I figured that it may be one of the following:

1. EMI / RFI leaking in. -- I have noticed that if I fiddle with connections near the devialet, I also start hearing weird feedback noises from the devialet.
   
2. Possibly it's just that the amplifier overheats and starts behaving erratically?
   
3. Regarding the cracking noise on the Bryston speakers possibly the D200 does not like 4 ohm speakers?
   

Anyways, any input that could help me zero-in on the problem is welcome
Thanks.