Roto Pasted into Nuke not matching

I’ve rotoed a few shapes in mocha, and then exporting using “nuke roto basic” - copy to clipboard.
And the shapes don’t match when sending to nuke, starts off fine, but towards end, it drifts downwards and doesn’t line up.

both mocha and nuke have same start frame 1001
both projects have same frame rate 24 and resolution 3200 x 1800

Mocha 2019 6.0.3 build 29
Nuke X 12.0v4
Mac OSX 10.14

any ideas?

Thanks.
Darren.