Lamanaria: can't interrupt Catastrophic Tidal Wave a second time?

Running the Battle of Dazar’alor instance Solo - Normal.

I’ve watched all the videos. I understand how interrupts work.

  • I get back to the docks after clearing the two mobs on the boats.
  • Start dps’ing
  • Successfully interrupt Lamanaria’s first Catastrophic Tidal Wave(CTW) spell.
  • Continue DPS
  • Kill the first two elementals that spawn
  • Continue DPS
  • A third elemental spawns, Lamanaria starts casting CTW spell.
  • I use the same interrupt that worked before at POINT BLANK RANGE
  • My interrupt is ignored and I die when CTW is cast.

I double checked that my interrupt went on cooldown. The SAME EXACT THING has happened on 5 different tries. His second CTW can’t be interrupted. I’ve watched numerous videos of players successfully interrupting. Seems that I’m doing the same exact thing but my interrupt after initially working is ignored the second time the boss starts casting CTW.

What am I missing?