IMC did a code change with the maintenance last week with the addition of the new Mystic Savior costumes. They made it so that if you change equipment that would cause you to lose access to a skill provided by items, the skill will instantly be removed from your hotbar. The skill will not come back until you put back on the equipment and manually drag the skill back onto your hotbar. This causes issues when you swap equipment, when you are disarmed in PVP, or anything that would cause you to no longer be wearing all five Velcoffer set pieces.
This change was done to remove the Mystic Savior’s “Transform” skill from your hotbar when you are no longer using the costume, however, it functions the same as Velcoffer skills in that it will simply grey out if you no longer wear the costume, and be unusable. I’m not certain why they believed this to be a problem to the point of changing this functionality.
I’ve made an addon to remove this and prevent the skill from being deleted from your hotbar. You can download it here:
Place this into your Tree of Savior data folder and restart your game. You can find that in the following location, typically, depending on where you installed Steam:
C:\Program Files (x86)\Steam\steamapps\common\TreeOfSavior\data
If and when IMC does a change/fix for this, this addon will no longer be needed and can be deleted. For now, this will work in the meantime to prevent this issue.
I hope it helps.