Hi @SMetcalf , we had similar issues and in our case was cache related (and from time to time we still have this issue).
Sometimes, hard reloading the page is not enough.
What we did is to add a “cache buster” when loading our files into HTML using a random variable or the timestamp. So everytime we load the page, we have our assets loaded with ?somenumber and that will stop the cache issue from happening.
This link might help: Add cache buster to Hubspot Hubl get_asset_url | HTML Code Copy | by CR Rollyson | Medium
Also, make sure you are using the latest CLI version (HubSpot CLI commands overview - HubSpot docs), we also had issues with CSS and JS files not being uploaded and it was fixed after updating our CLI.