We sent data of different lengths to the card through XDMA, and found that at certain lengths, stream XDMA will be prone to hang in the sent data. We used the script to call the official driver compiled dma_to_device and dma_from_device on our host platform on intel x86 I9. It is easy to reproduce the problem with 274 bytes of data on the KC705 development board. We still use the self-written driver and the K7325t board developed by us to still have this problem. We found that the problem and the length are very sensitive, if it is 264 bytes, it works fine. I also found that it is related to the PCIE slot inserted by KC705. If the PCIE slot directly connected to the CPU is easy to appear, otherwise if the slot is under the PCIE bridge, the problem is not easy to occur. We are using vivado 2019.2 + XMDA example (stream loopback) + i9 +KC705.