In SolidWorks, some assemblies reference "version -/5", this sometimes happens inbetween assembly versions. So between checking out, working on it in SW, and then checking it in, it loses its reference to a certain version of its parts. See screenshot below for an example. The way you can solve it, is by creating a new assembly version, putting the part as excluded from BOM, and then reversing it, rebuilding the assembly, and then saving it. This solves the issue, and then it looks like this: As