[subject change] DC offset in mixdown

My latest track seems to have developed an unwanted sound visible on the mixdown wav, which goes right through the track (you can see it best on the silent bit on the left in the screenshot), and it seems to have developed a bit of DC offset.

I cant actually hear this sound, even at loud volume, except when the track loops there is a click as the song enters the ‘silent’ bit, before the song starts.

What is this?! Is it the so called ‘watermark’ that certain plugin manufacturers claim to put into your audio?
I dont want it!!

ps: I have no plugins on the master buss.
audio-issue.jpg

Whats it look like zoomed in?

From what I can see (pure guess) it looks like some kind of high frequency thing!

it actually just looks like DC offset zoomed in, like the waveform which should be silence has been moved up a bit (offset).

My only suspect at the moment is the new Iron Axe guitar vst I’m demoing. I just put it on this track today and it ate about 30-40% CPU. I wonder how well it has been written.

Everything else is pretty standard I think.

I’ve changed the subject to more accurately state that I’m getting a DC offset when mixing down my whole track.

Anyone experienced this?