Burr Grafter is bugged in the following way: the pump goes through upon resolving the soulshift activation. If nothing is taken from the graveyard with soulshift, the pump goes through. If something is taken from the graveyard with soulshift, the pump doesn't go through.

The same bug seems to be affecting every soulshift creature, I've personally seen it with Pus Kami , Moonlit Strider and Scuttling Death to name a few.

To reproduce it clearly add 1 Child of Thorns, 2 Burr Grafter, 1 Scuttling Death and 1 random thing to the board. sacrifice the Child of Thorns to pump the random thing. Then sacrifice one Burr Grafter to try to pump that random thing, but soulshift the Child of Thorns. Pump won't work. Then sacrifice Scuttling Death targeting the random thing and return Burr Grafter. The -1/-1 won't work. Then sacrifice the second Burr Grafter, don't soulshift anything, +2/+2 will work. If it works for you, I swear I will make a video of it not working (I would have alredy but I can't find a proper screen recorder for XP).