When I set the 'Extend Executable Code' option and add a watch expression, running any code with 'Run Line and Move' jumps to the top of the file. Disabling 'Extend Executable Code' fixes the behaviour.
Atom 1.34.0, hydrogen-python 0.0.8, hydrogen 2.8.0.
EDIT: this is caused by watch statements being run through the expandCode method. The solution would seem to be to detect the origin of a statement and to not execute it in with code expansion.