Some parts have not approciate for your mesh setting.
1)Try to simply geometry.
2)Decrease mesh settings.
3)Exclude bolts, nuts from analysis.
4)Define bolt from connections.
5)Maybe use curvature based mesh can easiyle mesh your parts.
Keep in mind that the most accurate results are obtained by including all bodies in the assembly and using an optimal mesh size.
Simplify assemblies only if you are confident that the simplification does not alter the problem you are trying to solve significantly.
Before meshing there are some necessary thing needs to done on model.
1. Simplifying Model for Meshing.
2. By using connectors for modeling springs, pins, bolts, bearings, spot welds, edge welds, links, and rigid connections, you can reduce the number of elements in the mesh and save analysis time
3. Check Interference Detection before analysis.
4. Use of Mesh Control.
i solve that with incompatible mesh