Trying to record a volume envelope (I have just done two tracks successfully) however in recording the third track, the volume keeps jumping back to 0. I have not touched any controls or changed anything apart from the T command and then select volume envelope. Select the W on the track and record. Exactly the same procedure I have done for the past two tracks. Now all of a sudden this issue!
 
Any ideas?
 
Thanks

Offset Mode was initially on then turned off...or vice versa?  

There are automation write modes - depending on which version of Sonar different are available.
Overwrite, Touch, Latch - Artist only has Overwrite.
 
Behavior you describe is Touch mode.
 
It could be the third track just happends to be different in how you affect fader - and notice it.