Hello,
1] X-Particles 4
2] Arnold for Cinema 4D 2.5
3] Create a xpFluid simulation and have a sphere interact with the system by assigning an xpDynamics tag to the sphere mesh
4] Arnold IPR and final render do not update the position of the sphere which seems stuck in the original position. Other renderers (Standard, Physical, Corona) update the sphere's position properly.
scene: https://drive.google.com/open?id=1nnD9zv_JQP8TYIZWbiM8I_P8UPAo9gEF
If the above scene does not open please use this instead:
https://drive.google.com/open?id=1lCysbscloD5JKn20kH9czzmHNbzBzlVL
What's your X-Particles version exactly? I'm using 4.0.0642 which supposed to be the latest, and it does not recognize the xpDynamics tag.