This probably applies to Hide as well, but it will have to be tested further.
When spells are cast on a target with the Jump status, it usually missed automatically. However, there are some faulty checks at work.
When fighting an EvilMask (solo only), the game freezes up when it attempts to cast Haste on your party, Kain is under Jump status, and everyone else is dead.
Note: When the EvilMask is fought in a pair, apparently the Haste is retargeted to themselves... so it's probably a targeting issue.
This bug is fixed in FF4ET and FF4A.
There are also a few cosmetic bugs that exist here (when the party is dead and Kain's under Jump status)...
Spells are not being reflected off the EvilMask's reflect while in the air. (This always happens).
Some monsters don't bother to even cast the spell they normally cast in their battle script (see Warlock's Tornado, Zeromus's Flare, Kary's Embrace).
Some sounds are missing altogether (see Zeromus's Big Bang).
Some messages don't get posted (Pinkpuff's dance message).
The bulk of these are corrected in FF4A...
The spells are always reflected even though it auto-misses.
The spells are always displayed even though it auto-misses.
Zeromus's Big Bang graphics doesn't display (unlike the SNES version)...
Messages do get posted (like the Pinkpuff's Dance).
We have EVEN MORE themes now, but some old ones are gone...