moving one item in timeline moves keyframes on other items!

a new Title project.

I have 4 title/text items in a group, in staggered formation in the timeline.

-- group

-- item 1

-- -- item 2

-- -- -- item 3

-- -- -- -- item 4

I'm setting text style keyframes for each of the items; eg, Opacity, to fade in/out.

I'm very careful to select only the one item in the timeline that I want to work with.

I then move the playhead to the timepoint I wish to work with, add a new keyframe for the properties I'm dealing with, and change the properties.

but after doing this for all 4 items, moving any one of the items along the timeline moves not only that item's keyframes but also keyframes from other items, even ones outside of the group.

is there a linking function that I'm unaware of?

or is this a bug?

or...

any ideas?

Motion 5.0.7

OS X 10.9