Kassatsu sometimes does not apply the Critical Damage effect

Time: Between 20:10 and 20:30 CET
Frequency: sometimes (it happened twice within the particular time frame I've reported)
World name: Ragnarok
Character name: Ebi Frye
Class/Level: NIN 60
Party or solo: party
Area and coordinates: Neverreap

Steps:
1. I use a Ninjutsu, then immediately use Kassatsu
2. Mudras reset correctly, allowing me to use a second Ninjutsu
3. I use a Ninjutsu (I noticed it most often with Katon), Kassatsu isn't consumed, the guaranteed Critical effect is not applied
4. Kassatsu stays on for the remainder of its duration, then falls off

This isn't particularly new and I have observed instances of this bug happening ever since ninja has been introduced. For some reason, this has become more frequent for me after the EU data center moved to Europe, and then the frequency happened again after 3.3 so my guess is there is a chance it might be related to low latency and Kassatsu's lenghty animation.

Connection Specs
- Cable, Bouygues Telecom