Strangely enough I checked it again and it is gone now. I didn't change a thing. Also the CPU was not overload since I was using the delay block only. Also I wasn't using high feedback setting.
Would be nice to know what is was anyway.
Maybe not what you encountered, but something to remember: XFADE TIME being too low will cause clicks. Just going from 1 ms to 2 ms gets rid of a bunch of high freq. content; improvement is more subtle beyond 2 ms. It's probably best to avoid settings below 10 ms, the default.