I’m using it since a few days and noticed a slight level difference in L / R
Even entering in mono the L output is always a little bit quieter.
I just adjusted my mixer levels but then I was wondering if there are other cases and fount this thread.
I was hoping for a calibration procedure or something.
I investigate it and had an exchange with Elektron support.
A little difference between L&R is inevitable with drive circuits.
But what bothers me the most is that it generate lot of phase.
I use an imager and it’s visible.
If it was only a panning problem, the imager would show a straight line leaning on one side. But it show that the Heat produce some phase when the drive circuit is engage.
When sending a white noise to the heat the comeback signal is centered and have a low phase reponse. But, when I use a low frequency sinewave, the output become out of phase.
So it depend a lot of the material injected.
Elektron support told me that they are working on an update adding a user setting for manually adjusting the balance when needed 
I’ve also had this issue, tho for me the level differences have been considerable. Only choosing a preset or restarting the device fixes it