Is it a custom web resource created by you or something part of a managed solution?
Can you check the dependencies of that file?
When adding that file in a new solution, uncheck all the dependent components/assets to avoid such behavior.
Are you editing that web resource from form editor, I noticed the solution getting the entire entity added when doing so (CRM 6th sense). You can remove the unnecessary components if you really don’t want to be part of that solution before exporting.