When you create volume envelope and then stepper device and you set it to / (divide) -> sound will stuck and looped sound will never fade out.
Btw. what the stepper device is best for?
It’s not hard to have an infinitely playing voice - just need to put devices together in a way that makes the final value higher than zero.
Which is ofc. not so great if you don’t discover this, but really I think that’s what happened here.
But before we can rule out a bug (stuck?), you would have to share your example.
Btw. what the stepper device is best for?
A lot of things 
I have primarily used it for panning stuff like hihats - you often want them to be alternating between left and right. Stepper is perfect for doing this with minimal effort (just two steps, slightly above/below the pancenter). But also just adding a more controlled flavor of randomness (by assigning step to random, you get a randomly chosen value from a predefined set of values).
Or you can hook up a macro to the reset and use it to switch between values… many uses here.
So, I guess Stepper you could say is conceptually close to the “custom LFO” device.
WIKI entry
http://tutorials.renoise.com/wiki/Modulation#Stepper_.28Redux_Only.29
I cant replicate it. But there was now other way than deleting redux to stop sound.
Thank you for your tips about stepper.
I will render this if i will encounter this again. Until that this topic is redunant i guess 
(Random chosed values? Stepper can behave randomly?)
Hm, I wonder if sending an CC#123 (All Notes Off)could have saved you here?
In any case, having infinite voices is quite possible, also in Renoise 3.0 - have to be careful about those.
I once created a sound, couldn’t understand why it was so taxing on the CPU. Until I realized that there was a very, very tiny amount of sound still being output, constantly in the background.
Since then, I have adjusted the main VU meter in Renoise to -96dB (rightclick to change).
This will most likely reveal any such tiny things…useful tip, perhaps.
(Random chosed values? Stepper can behave randomly?)
Yes. Quoting from the Wiki:
Step: The number of steps taken every time a note played. When the value is reduced below 0 it becomes Random.
Happens to me every time with / and a zero value in the stepper.
Happens to me every time with / and a zero value in the stepper.
Not sure what you guys are referring to. Division by zero!?
Does the sound freeze, or something like that? Share the preset?
I cant replicate it but deleting steper or setting volume main operator to 0, nothing stopped that sound. Just deleting redux did it