Repro steps

1. Load save game (Terran Carrier Test.CG3Sav)
2. Select fleet "Terrans Fleet 17162"
3. Move to adjacent Ship Graveyard anomaly
4. Yes - engage them in battle
5. View Battle
6. Battle Summary indicates pirates lost 2 units, Terrans lost 0 units
7. Return to strategy view

Expect: Terran fleet still alive, anomaly explored
Actual: Terran fleet destroyed, anomaly intact

Note: Selecting Quick Battle results in expected behavior

Savegame link:

https://1drv.ms/u/s!AjQNX_0pj-ibg7xHlAUxAyiLmXovCg