I noticed that particles when applied to entities are doing some strange things.
The speed of the particle is way to fast even setting the speed to 0.001 it seems to ignore the speed control.
The other issue is that the particles are not going straight up like normal they are going on an angle.
I did not see any errors out of the normal form the last run game, and the game is not crashing so I am not sure what is causing it to speed away like that.
I tried increasing the position of the particle on the Y axis to try to fix the issue thinking it may be getting stuck in the entities hit box but it seems to be spawning on the hood of the car or in the same spot still its hard to tell where its coming from with such height speeds.
For the version its on the latest patch for 1.14.4 / 2020.2 other than that I am not sure what would be the root cause of it :P
If you need me to test anything on my end let me know below :)
I can confirm the speed parameter has no effect.I will rename these d* fields to v* too.
For now, use dx, dy and dz to set x,y,z speed. To make particle fly upwards, set dx and dz to 0 and dy to the desired speed.
I will fix this to make speed control the speed and d* control the area in 2020.3.