To reproduce:

1. Open attached project and attach script 'move ship' to the spaceship gameobject
2. First play scene with the script unchecked. This shows a small unmoving blob
3. Play scene with the script checked and "Move With Physics" box un-ticked. The blob will move in circles
4. Now tick the "Move With Physics" box and observe that some particles will 'fly away' or disappear from the scene in the beginning

This is also repro in 3.5.1 f2