Not a bug
There is a cool down check made which prevents a pc from having to contend with stacking/overlapping aura checks. How it works is below.
Current Cooldown: 5 rounds though NWN engine tracks it oddly in how actions are ordered.
PC enters an aura
Check is made and results (success or failure) applied
Check is made to verify if in the cooldown period. If yes, no check. If no, run another fear save and record.
I've had the cooldown adjusted via Echo v8567 to 6 rounds to give a bit more time for players to react before a new fear check.
Remove Fear will remove all fear effects and provide a +4 to fear checks
Protection from Alignment (varies by level and some feat but minimum is +5
Clarity protects against all mind-affecting effects (fear is one)
Closing and moving to Implemented suggestions