We moved from _cts templates to a centrally stored template in _layouts some time ago but noticed recently that newly created site, for example with using New-SPSite, gets old content type templates in the ResourceFolder. The DocumentTemplateUrl is correctly assigned but many old versions of the template are stored in _cts/ContentTypeName.
I have cleared all old files out from _cts but still when a new site is created the files appear in the new site. Where do these files come from and how can I get rid of this behaviour?
The content types and _layout template is working fine but the clients environment got hundreds of content types so the footprint of each site is huge due to all the old templates. We are taking hundreds of files in the recycle bin of a newly created site.