Steven Vue

U can't link a fishing rod hook to player normally.
Instead...
Use command blocks and...
Create a redstone clock
/fill redstone_block ~-1 ~ ~ ~-1 ~ ~3
/fill air ~1 ~ ~ ~1 ~ ~3
Then...
/scoreboard objectives add fishing stat.useitem.minecraft.fishing_rod
That will test if a player is using a fishing rod
Then to link the player to the hook
/scoreboard objectives add hook dummy
/execute @a[score_fishing_min=1] ~ ~ ~ /scoreboard objectives set @e[name=unknown] hook 1
The execute @e[name=unknown,score_fishing_min=1] what ever you need to connect the player to the hook for
Then reset the the scoreboard

I have the same problem when I use the command
/summon FireBall ~ ~ ~ {Motion:[0.0,0.0,0.0],direction:[0.0,0.0,0.0],ExplosionPower:1]
My game crashes also this happens when I summon some other mobs