repeated use of ctrl-O in a sub-list moves the whole document downward

Showing/hiding completed items in a sub-list (where the sub-list has completed items at the top), via the menu works as one would expect:

show: the sub-list expands downward

hide: the sub-list collapses upward

But when showing/hiding completed items using ctrl-O, and the cursor is in the sub-list, the behavior is unexpected:

show: the sub-list expands downward

hide: the sub-list collapses downward.   I.e. the sub-list stays where it is and the document above collapses down onto it.

When using ctrl-O more than once, this has the effect of slowly moving the entire document downward.  This is ... annoyingly inconvenient; I keep having to scroll down just to move the sub-list back into view.