Phasing / comb filtering problem in non binaural mode

[MOOGelPackung]

The issue is not really new!
Look here:

Phase issues in non-binaural mode (not summing to mono cleanly)

When using non-binaural mode it always sounds hollow / phased in a weird way when summed to mono (thought it might be the sounds I was making but it happens with the raw oscillators). Initially thought it was my unit but tried another one out at a store and it had the same issue. This is the weird thing - when I try using it in mono mode (only plugging into one output) the phasing issue happens with the left output, not the right. Has anyone else noticed this?