If the ms is the work of a copyist, then of course "Shreave/ streave" and "eering" may have resulted from misreading rather than from "tradition."

The simplest rationalization for "Shreave/ streave" might be " 'Tween," but it is hard to imagine a copyist getting that wrong.

I still have no suggestion for "eering."

How bad was Buchan's handwriting generally?