Based on how far away you move GPU particle away from the center of the world glitches become more extreme.
The main one is that the particles system disappears when you come close to it. the further the particle is placed away from the center of the world the less you need to come close for it to disappear.
The 2nd one is that it dissapears based on certain angles.
Easy to recreate:
Just create a new particle system and make it a gpu particle system, do that required fixed bounding box setting for it and adjust the values, values don’t matter for the bugs.
Place the particle in the world
set transform to something like 1000,4000,8000, that should show you the angle glitch
set transform to something like 0,0,5000 that should show you the distance glitch
Edit: this even happens when GPU particles is inside a blueprint on 0,0,0 but the blueprint is moved away from 0,0,0 in the world. So, GPU particles are basically currently totally broken.
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I have attached my test project as I am not seeing what you are describing above. From me it sounds like your Fixed Bounds are not being set correctly. In addition to the Set Fixed Bounds Dropdown there is also a Detailed Set Fixed Bounds Section in the Particle Details Panel (Click in the Black space to the right of your emitter will get your access to those settings.
Check that and if you are able to make changes to the test project to replicate the issue please repost the Test Project with those changes and we will continue our investigations.