I have noticed that sometimes when I brush a mask on an image that has either had perspective corrections applied or that have had lens corrections applied (corrections that Nitro has been trained on, not Apple-supplied corrections), that the mask is shifted on the image. It seems to apply the mask to the uncorrected image. This can make a difference where some significant corrections have been made (e.g. shadows of objects in the sky). I guess that this is down to the image processing pipeline. Is there any way round this other than exporting an uncorrected image for lens distortion and then manually making the corrections?
I am able to reproduce the problem with brush strokes and lens correction. However, when I apply perspective, the brush mask seems to follow the image correctly. If you only have perspective on an image, do you still see a problem? I have logged the bug with brushing + lens correction.