This was posted a while ago on the cow forum. Can anyone verify it's not just me 
- feels like a serious bug.
When I use the Render Queue to export a comp to MXF OP1a AVC-Intra Class100 1080 I'm getting a settings mismatch warning that my comp has to be resized from 1920x1080 to 1440x1080 with a PAR of 1.00. Once exported my entire comp is squeezed into a full 1080 frame (1920x1080/1.0PAR) but with a black border (it's shrunk 133% inside of 1920x1080). AVC-Intra Class 100 is supposed to be 1080 full raster and to be sure Adobe Media Encoder works just fine. I'm getting the same result on 2 PC's and a Mac all with current updated AE. It seems to be rendering the footage based on a 1.33PAR and scaling it down. The comp footage is the correct aspect (1.0PAR) inside this black border.
MXF ACV-Intra Class 50 1080 from AE is 1440 with 1.33PAR as it should be.
Just wondering if anyone else has experienced this. Again, it works fine importing the AE Comps into AME then out to MXF AVC-Intra100 (everything 1080/1.0PAR as expected with no warnings or errors, looks correct in the AME preview too).