Fragments (or rather BopAlgo_Splitter) creating new objects

Hi all,
Newbie here,
I am working on a tool to help with creating geometries from CAD for particle transport, and I've run into a few problems.
The way I'm working is I export my model from CAD to a step-file, then this is converted to a tesselated geometry from a python-layer (OCP which is simply a thin wrapper to OCCT). My problem is that I often have objects that share surfaces, and for particle transport to work it is imperative that these interface surfaces have to be identical. To ensure that, I perform a BOPAlgo_Splitter operation, which will allow me to create a single surface mesh for a shared surface which can be reused. This often works fine, but can in some cases this can create additional Solids out of thin air.

Has anyone else experienced this?

cheers
Erik