As far as I recall, this is a known issue, although I could not locate early postings discussing this issue. What happens is that proxy cache makes use of the first item in the filter to discriminate between responses. In your filter template, the first item is the objectClass equality, which means that any filter with that objectClass value, regardless of the uid value, is treated as a duplicate of the first one. If you reverse the order of the equality filters you'll get the expected behavior. There should be another open ITS for this issue, but I can't locate it right now.