It was always loosing the contact on the amplifier side.
It was between the banana and the WBT speaker plug on the amplifier.
Don't know why. I have no clue.
I was having issues with the sound consequently and had to plug out and in again the bananas to get back to normal. And this once a day at least. (has it ever been normal by the way?)
Since I use spades, this problem is not recurrent anymore.
So this is my opinion and conviction not to use bananas anymore whatever convenient it is. Finally, I don't need to plug and unplug every 2 hours. So what is the point of this so called "convenience".
What is the reason some people find these banana plugs "convenient" ?