Buff Cooldown not Updating Correctly

Time: 8:23pm AEST, GMT +11
Frequency: 100% Reproducible
World name: Gilgamesh
Character name: Astral Faerie
Class/Level: Dragoon/Monk 60.
Party or solo: Solo
In-game time: N/A

Housing: Ward 8 plot 19 Goblet.

Steps:
1. Use a class change hotbar skill + shared/cross classed buff in question.
2. Click to change class then use the skill.
3. Class changes.
4. Attempt to use the buff on the other class, can't because it has been used but the buff duration is still ticking.

Connection Specs
- Type of internet connection/provider: ADSL 2+ / Telstra
- Modem maker/model number: Netgear Nighthawk r7000

PC Specs -- N/A

Video Example -- https://www.youtube.com/watch?v=90DwEHRQ1os