I have a step file which is an assembly. When I import it I need to save the parts as well, but the parts saved from this step assembly do not have thumbnails for preview in file explorer.

Here is an example using files from SW tutorial(SOLIDWORKS 2019\samples\tutorial\assemblymates). The parts and assembly have preview thumbnails in file explorer. 

But when I export it as step, import it and save them again, only the assembly has preview.

Since the original files have preview, it should not be the problem of preview setting. I think it's likely at the import settings but don't know which term affects it, so I attach my setting as well. 

Does anyone have any idea? Thanks

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Solution:

Use Task Scheduler or #TASK to update all the files instead of doing it manually.