i had problems with send effect channels several times now under linux.
after some time the audio functionality of renoise stutters shortly and then there is no sound anymore.
after a restart everything works again. this problem only comes up when i use send channels.
attached you find a file which triggered this bug. i use a script to start all the tracks so there are no notes set inside.
what infos do you need else? im on ubuntu 13.10 using jack.