Grouped fields scrolled out of view sometimes act as if visible

[depstein at att.net]

It appears to me that for purposes of dragging and dropping text, MC treats grouped fields scrolled out of view as if they were visible.

Recipe (MC 2.5 Mac OS9):

Create 3 fields on a small card.  Field 1 occupies the right half of the card, field 2 the left half of the card, and field 3 is on top of field 1. 
Group fields 2 and 3, give the group horizontal and vertical scrollbars, and resize the group so that it covers only the left half of the card, revealing field 1 on the right half of the card.  
Drag the group's scrollbar all the way left so that field 2 is visible, and field 3 is concealed (off to the right).  Type a word in field 2;  then select it and try to drag and drop it into field 1.

Result:  the word gets dropped into field 3 instead.  MC seems to think field 3 is "on top" even though its group's scroll conceals it from view.

Monitoring messages and offsetting the field positions slightly reveals that field 1 does not get a dragEnter message unless I drag into a part of field 1 that extends beyond the implicit rectangle of field 3.  You can also see that the "skittering insertion point" that a text drag normally causes in an unlocked field does not appear in field 1 as long as the mouse is over the implicit rectangle of the hidden field 3, but appears if the mouse moves beyond field 3's hidden edge.

For other purposes,fields scrolled out of view behave as I would expect a hidden field to behave.  For example, a handler that puts the target on mouseup reveals that field 1, not the hidden field 3, properly receives command-clicks.

Do others get the same result, or have insights or remedies to suggest?

Many thanks.

David Epstein