clone command of 3969 blocks crashes minecraft

What I expected to happen was...:
Clone an area of blocks one block into a specific direction. You know, like a flying machine Included is a testforblock command a clone command and a say command. It happens randomly but very often.
The excact commands are:

testforblock ~ ~ ~8 minecraft:air
say tp south
clone 7348 22 1017 7368 30 1037 ~-10 ~-1 ~-14

Wierd behavior is that cloned items are also dropping randomly. For example redstone or beds don't work if they are close to each other. This behavior seems connected to the direction everything is cloned.

What actually happened was...:
Crash to desktop.