Exporting XDCAMHD with black bar Pixel Problem

I export my video by MXF OP1a format with XDCAMHD 50 PAL (4:2:2) codec
Field Order is Upper First
and I got a black bar on top and bottom to get my video aspect ratio in 2:1

But when I finish export, I found that the pixels near bottom black bar crashed a bit
Is it happened before or any solution?
Thank you!