Unable to use Free Cure (or II) if your remaining MP is less than cost of the Cure II

[HEC]

Unable to use Freecure (or Overcure) if your remaining MP is less than cost of the Cure II (or Cure III)

ISP:
N.A.

Type of Internet Connection:
N.A.

Internet Connection Speed:
N.A.

Date & Time:
Any time

Frequency:
Always

Character Name:
M'ete'leskum B'leskum (but same with other characters)

Race:
Hyur F (but same with other characters)

World:
Moogle

Class/Level:
WHM lvl 50 (but was happening with lover levels as well)

Area and Coordinates:
Anywhere

Party or Solo:
Both

NPC Name:
None

Monster Name:
None

In-Game Time:
Any time

Steps:
1. Use Cure (or Cure II) until Freecure (or Overcure) status is reached AND at the same time the remaining MP is less than cost of Cure II (or Cure III)
2. Try to cast "free" (e.g. zero MP cost) Cure II (or Cure III) while the Free Cure (II) status is still active
3. Cast will fail as it checks for remaining MP (which is less than cost of the spell) despite it being free / no MP cost

This is fairly annoying bug as at the point where you'd need the Free Cure most (after exhausting most of your MP during the "heat of the battle") you're unable to actually use it.