Hi,
it is known that you can’t use an additional Basic Auth in front of ownCloud for the simple reason that oC is using an own Basic Auth in various functions like those shared links etc.
You can’t have two basic auths (one by apache and one by ownCloud’s WebDAV). If it has worked, it worked by luck, as the behavior of a daisy chained basic auth is undefined.
→ 1.5.3: Basic Authentication Support Broken · Issue #1618 · owncloud/client · GitHub