The fuzzer found this issue. Iterator API and block-based API return different results when decompressing a Date (which uses deltaOfDeltas). The differences begin when we load a new simple8b delta block, after decompressing a whole previous delta block. In the block-based API the deltaOfDelta value is 0, so all of the decompressed values are decremented by the same amount. In the iterator API the deltaofDelta value is not 0, so the decompressed elements are decremented by different amounts.