Testing the connections on the BL6000 is not easy but the MX6000 is straight-forward. (Lay the 6000s flat and fiddle around with the connection. Maybe taking the foot off will help? Also play swapsies with the cable and channel selection. 1 cable. MX PL1, BL6000 PL1, switch pos 1 and 2, repeat for PL2 on the same speaker etc..... Go methodically through all the combinations of MX-PL connect, cables, channels, L/R speaker....if it persists throughout - likely its the MX. Maybe you get lucky and its a broken Powerlink cable? With the age of that equipment there may be a possibility that there is an internal component near failure? A Cap perhaps? Once you have done logical swapsies and no clearer on the answer, its better to take it into a repairer who is familiar with servicing older B&O to see if they can lock down the fault?

Thank you very much for your answers !  so it may also do that if c7 powerchord and mk2 cables are 1st price quality ? Again it's only when i'm near and otherwise the sound quality is great, i just fear it may cause damages in the long term

I dont think the power cords are an issue. B&O has always packed cheap power cords and Ive found that they are reliable. As to the powerlink, I guess it depends who made them? Genuine B&O and soundsheavely cables are reliable. If it was the wrong type (I think with ICE-Powered Beolabs...you will get a hum. Not a crackle. However, if something has been strained or compressed - it may leads to problems. I would not discount that your equipment is old and has worked a long time. A lot of B&O - particularly at that age can be serviced. As I said above...I would be surprised if you did Service the TV...a Capacitor or two may need replacing?