[LAU] Audio seeping into another track

This might be not/so/easy to prouve although a number of screenshots should. I have a guitar track that has a pre-fader send to another track that adds delay. Then there is an audio drum track that records what has/is played on a MIDI track that is in contact with a Korg Microstation. There are no connections between the drum and guitar and delay tracks, I have double verified in qjackctl. All of those tracks go to the master bus. When the drum is played there is echo added to it from the echo plugin of the other track. Taking out the echo plugin results of having no more echo on the drum track. I will continue to see what is going on. meanwhile, has anyone experience such a behaviour in Ardour (4.4.0) ? (Ardour 440, ah! :) Cheers.