Breaking change in hugo 0.123
a html file in a bundle is a page resource and now page resources won’t be copied consistently.
you will have to manually publish your html files in the called template (usually single.html)
{{ range .Page.Resources.Match "**.html" }}
{{ $publishPath := urls.JoinPath $.RelPermalink .Name }}
{{ (.Content | resources.FromString $publishPath).Publish }}
{{ end }}
Solution taken from: