AutoCAD Inventor :: DWG Sections Disappear

We're using Inventor to model complex bridge structures. We take sections, plans, elevations etc. from the model to AutoCAD.dwg format. We then open the .dwg and insert the view blocks in model space, these files are then used as xrefs in AutoCAD, long winded but a supply chain requirement.

The models and xrefs are all saved on our network, no vault used, no windows syncing.

To create the sections we have a separate part file that contains sketches where we want the sections taken, this is placed in our assembly. The sketches are all straight lines (no cranks) and included in the .dwg and selected to create the sections.

We're experiencing a significant number of files that when we open to update the model views we randomly get an error "valid section line not found" and several of the sections disappear. The section lines part file is fine, the section lines are all still there and unchanged.