blue mage spell number 14 unacquirable

[Loevve]

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Date & Time: Always
Frequency: Always
World name: All of them
Monster name: Manor Sentry (in boss battle, boss name: Lady Amandine)
Class/Level: Blue Mage
Area and coordinates: Haukke Manor Final Boss
Steps:
I guess I will just make a summary cause it is less steps and more of just when the game was patched, it seems the mob in question was changed in a way that makes level 5 petrify unacquirable. The only known way to acquire the spell that i've been able to find by searching the internet was by getting the boss Lady Amandine to roughly 25%, she would spawn Manor Sentry, and then you would drop it to roughly 25%, and wait for it to cast the spell, and kill it. Due to you having to kill the mob after using the ability to acquire the spell, this was the only known way to get the spell. From searching the internet the Manor Sentry appears to be the only known mob that used level 5 petrify. Manor sentry no longer spawns in the fight as an attackable mob that you can kill, or even get to use level 5 petrify. How are new Blue Mages supposed to get the spell? I may be wrong, and it may be possible to get them to cast it, but I don't want to waste a lot of time trying to test something at this exact time that seems like a glitch/oversite. If you can just confirm you can still acquire the spell the same way as the below video, or can direct me in another way to acquire the spell I would greatly appreciate it.
https://www.youtube.com/watch?v=IpwThxwlYgQ

[Jeeqbit]

The enemy is now outside the first boss room and still casts the spell.

[Charlotte_Wells]

Try to do it on a level that you can divide by 5. like 50, 55, 60.

(Level 5 Petrify as well as Level 5 death only work when the target level is dividable by 5
and in the past FC members with the same issue had more succes after leveling up.

[neola]

I believe as long as you are present when the spell is used, it can be learned, if the dungeon is level synced it should provide 100% learning.
Please wait for the enemy to use the "level 5 death" ability first, then kill it. If level synced it should grant the spell 100%