Hi Seren,
This is what I find in the docs:
https://ephere.com/plugins/autodesk/max/lucid/docs/1/Collision_Objects.html
"To preserve the stability of simulation every scene has a default global "sandbox" volume. If any of the simulated particles try to venture beyond its limits they will be stopped by this volume. The default size of this object is 10,000 scene units.
If you create a sandbox collider object described below, it will override the default sandbox volume. Therefore, you can increase or decrease the size of the overall simulation scene by defining your own sandbox collider. "
This may help you to increase the limit of 5000cm. I don't have too much experience with Lucid so I have passed this on to Marsel, he should be able to help you better. :)
Jeordanis Figuereo (Product Designer. EPHERE Inc.)