1st Boss of Pharos Sirius stunnable 4x in a row

Time: 4:55pm
Frequency: 3x so far
World name: Hyperion
Character name: Neon Zero
NPC name: N/A
Monster name: Symond the Unsinkable
Class/Level: PLD 50
Party or solo: Party
In-game time: N/A
Area and coordinates: First boss room >.>
Steps:
1. Stunned the boss 3x in a row for the full duration.
2. Giga Slash was being cast and I forgot stun was on immune but instinctively stunned.
3. The boss was stunned and unstunned within a halfsecond (floating text) even though he should be immune at the time.