Strange Question Regarding Monsters

[TheDevoidLife]

I have a scene structured where several small boxes stacked go flying down a hall, revealing a grunt behind them, which then chases the player. However, upon having the boxes go flying, the monster does not move. I've checked debug messages and I get several regarding monster health. So I looked into it a bit and found out that the monsters can indeed die(i.e. just stand there, practically unable to do anything) if they receive enough damage within a short time. Basically my question is this:

Is there some way to prevent the monsters from taking damage, or fluently position the monster at just the right time?

Additional Notes:

• The monster chases the player beforehand, but he moves just enough boxes to get through, while still barring the monster's way, so he's already standing behind them by the time it happens.
  
• The player is forced to look at the boxes, which go in the opposite way of the player.
  
• The player is supposed to be caught by the monster and die
  
• It seems to be a bit random, dependent on where the monster is standing, but most of the time he ends up 'dying'

Thanks in advance for any help, I know the question is a bit unusual.