If it fails to load the CSS entirely, it's not this, just general network problems. Truncation "shouldn't" be common, because chunking is very common for mains

If it fails to load the CSS entirely, it's not this, just general network problems. Truncation "shouldn't" be common, because chunking is very common for mainstream web servers (and clients of course). And TLS is supposed to explicit protect against this regardless of HTTP. OTOH, especially behind proxies there are a lot of very minimal HTTP implementations. And, for one reason or another, it is fairly common to visibly see truncation for images and occasionally for HTML too.