Casting interrupted by redzone move even when outside

Time: Often
Frequency: Often
World name: Hyperion
Character name: Calyanare Vendaurel
NPC name: n/a
Monster name: various
Class/Level: happened continually while leveling BLM, so I'm pretty sure the level is unimportant
Party or solo: both
In-game time: any
Area and coordinates: any
Steps:
1. Start casting something.
2. Enemy casts move that causes a red area to appear on the ground.
3. Interrupt cast, move out of red zone, re-start casting the same spell.
4. Red zone disappears, animation occurs. No damage is taken, but spell is interrupted as though you had taken damage.

This appears to happen with moves that would have interrupted the cast if they had hit you (a Megalocrab's Bubble Shower, for instance). Even if you dodge the move and take no damage, you still get interrupted. It doesn't happen every time, but appears to happen most often if you interrupted a cast to move out of the red zone and then are casting that same spell when the attack finishes.