I've tried looking at the export_descr_ancillaries.txt file but everything seems to be in order. Not sure what's causing the bug.

Anyway here's the trigger:

Trigger trigger_roman_turncoat
WhenToTest PostBattle
Condition WonBattle
and PercentageEnemyKilled >= 40
and GeneralFoughtCulture roman
and IsGeneral
AcquireAncillary roman_turncoat chance 8


The trigger for easterners is of a similar format:

Trigger trigger_easterner_turncoat
WhenToTest PostBattle
Condition WonBattle
and PercentageEnemyKilled >= 40
and GeneralFoughtCulture eastern
and IsGeneral
AcquireAncillary easterner_turncoat chance 8