Boadt, Lawrence, and Celine M. Allen, eds. The Paulist Liturgy Planning Guide: For the Readings of Sundays and Major Feast Days. Vol. A–C. New York; Mahwah, NJ: Paulist Press, 2004–2007. Note these have the same problem:
- Wallace, James A., Robert P. Waznak, and Guerric DeBona. Lift up Your Hearts: Homilies and Reflections for the “C” Cycle. New York; Mahwah, NJ: Paulist Press, 2006. (and others in series)
- Donovan, Daniel. Preparing for Worship: Sundays and Feast Days—Cycle C. New York; Mahwah, NJ: Paulist Press, 1994.(and others in series)
- Bergant, Dianne. The Word for Every Season: Reflections on the Lectionary Readings (Cycle C). New York; Mahwah, NJ: Paulist Press, 2009. (and other in series)
I would expect this resource to have the liturgical calendar milestone only once per entry - the heading of the group where the arrow begins. I would not expect sub-items to repeat the milestone. I would expect the Bible passage to have milestones appropriate to the Bible.

Note I check only one liturgical date. The same issue likely exists elsewhere. This error has not been noticed most likely because one cannot do a milestone search from the Context Menu and there is no Guide section that uses the index. I hope that will be changed in a future release (near future).