I've encountered strange proxy exporter behaviour when tried to export one model. The model is made of several objects, grouped into single group. Exporter settings was, collapse and export to single proxy - on, replace source objects - off. At first try, it exported model only partially, missing pieces was simply duplicated separately as meshes. I decided that this is the model's fault, since it's quite old and messy, so i went through all objects and collapsed all modifiers except turbosmooth and reset transform coordinates. After that the model exported without issues, but for some odd reason, the original model was completely ruined in process - many objects were duplicated several times, some were merged with each other and assigned wrong materials. Luckily i saved scene before export, otherwise i would be screwed o_O
Exporter version v0.06