Missing style.css after change default theme

I did login as admin and change favicon, login image, name and slogan in settings -> theming

#1 It was strange because it did not work smoothly. But after few minutes I did get correct result.

#2 anyway, I still get this message in log

[error] 547#547: *2364 open() "/usr/share/webapps/nextcloud/apps/files_markdown/build/styles.css" failed (2: No such file or directory), client:, server: nextcloud.local_domain, request: "GET /apps/files_markdown/build/styles.css?v=637e04f2-13 HTTP/1.1", host: "nextcloud.local_domain"

I get that one always when switching to FILES app.

should I create a new bug?
is there any solution?