I've created simple 7 seconds clop which uses standard plugin for FCPX: "Bold Fin" title.
While i am editing this clip - everything fits to the screen:
also everything is ok when i am starts to export this clip to the master file:
but when actual file is ready - it seems like it is cropped:
Could somebody please help to find a reason why my output actually cropped? And how fix this issue?
Judging by the image you provided, you have non-square pixels in your footage or in projects settings (or footage's aspect ratio isn't 16:9). I print-screened the image inside FCP's canvas and found that you have rectangular pixels stretched along X axis, instead of square ones.
Seemingly, FCPX trying to compensate pixel aspect ratio for FullHD export (par = 1.0, ar = 16:9), stretched pixels along Y axis, which led to cropping.