From what I could find on the web (archives) for USAAF A-20 units on 19 July 1944:
409th BG: Railroad bridges & fuel dumps (St Hilaire de Harcourt?)
410th BG: Fôret de la Guerche fuel dump
416th BG: Bruz Fuel Dump, S. of Rennes (see
https://www.416th.com/missions/mission102.html)
These all seem to be more in the Rennes region?
Regards,
Leendert