Grimrock

1. Sometimes Wyverns vanish and reappear when flying from one square to the next rather than animating normally. I've usually observed it from the following position: W = Wyvern
D = Wyvern destination square
P = Party, facing north

2. Sometimes the damage blood splatter an number on your party members reappears after the damaging event.
For example, you fall through a pit. Then you walk a few squares and maybe click on an item in a character's hand. Then suddenly the blood splatter with the damaging event appears on him again. I don't think it actually does the damage again, but merely displays the blood splatter and number again. I think some action on my part triggers it somehow, like going to sleep, mousing over the character or picking up an item from his hands.

If you have the spell runes up while taking damage, after finally putting them away the damage shows, could it be that?

Just tried it a few times and you're right. By opening the spell rune tab and jumping down to a pit I can reproduce the bug easily. There's no blood splatter initially when I land but as soon as I close the spell rune tab it shows that I'm taking damage even though I'm not. The pit falling damage splatter somehow gets stuck until I remove the spell rune tab.