Your publisher is wrong.
These messages are warnings from Chrome DevTools. It tries to download source maps for minified javascript files when you open DevTools. It seems Yandex doesn’t provide source maps for their private SDK, i.e. the files are absent or the URL to the source maps are invalid. That’s why you see these warnings. And they don’t affect the game in any way.
Does your game not run well because of these messages in Chrome DevTools Console?