The issue has not been resolved in the latest release of the Kona drivers (6.0.2). Oddly enough, there are specific "DV" framebuffer settings listed for PAL resolutions, but not for NTSC.
PAL settings include:
AJA Kona 625i25 10 Bit
AJA Kona 625i25 8 Bit
AJA Kona 625i25-DV 10 Bit
AJA Kona 625i25-DV 8 Bit
But the NTSC settings do not include the "DV" versions:
AJA Kona 525i29.97 10 Bit
AJA Kona 525i29.97 8 Bit
The "DV" suffix in the framebuffer listings denotes a field shift correction for interlaced 720x480 comps, which require video output to be shifted up or down by one field in order to preserve proper field order on playback.
A fix for this issue was promised back in November for the 6.0.2 release, but apparently it didn't make it in.