Code splitting practice using CDN
Your main problem is that you're flushing the CDN when you're deploying a new set of artefacts, which will effectively ruin anything still in progress (whatever its state). You should add the new artefact versions and leave the older ones in place, at least for as long as your published cache lifespan for the top index.html file is. 

This way even if users look at an older (cached) version of the page which references other older version artifacts they'll still be able to download them (users have no clue that a new version is available as the cached version is immediately served as long as it's not expired). And whenever the cache expires users will get the new version of the top page, with the references to the new artefact versions.