To reproduce it I just attached a lead to the Happy Ghast and started flying arround in creative mode.
/attribute @n[type=happy_ghast] minecraft:flying_speed base set 1
/attribute @n[type=happy_ghast] minecraft:movement_speed base set 1
These commands are supposed to change the Happy Ghast speed but they don’t (this may be intentional but would be a great feature to add)
To be honest I don’t really know (I tried to reproduce it on another pc but it doesn’t crash)
As for how I created it:
/summon happy_ghast (I then put an harnest to it)
/attribute @n[type=happy_ghast] flying_speed base set 10
/attribute @n[type=happy_ghast] movement_speed base set 10
(this way you can have the exact same Ghast as I have, but the values doesn’t change anything on the Ghast, he has the same speed)
And then use a lead on him and fly around.
But as I said I can’t reproduce it on my other PC, so giving you the specs of the PC on which it crashed may be helpful:
GPU: AMD rx 6750xt
CPU: AMD Ryzen 7 7800x3D
RAM: 32GB DDR5 (2GB on Minecraft)
The game was running on a NVME SSD.
I don’t know why this has happened to me twice on my computer but not on the other one, I you have any other question please do.