I using NX8.5 Version. Animation speed has been improved in NX8.5 Version.
But We want to slow down the speed of the animation.
this performance behavior is a known topic and I assume you refer to the "Replay" tab.
Less what you can do, but you can check if your graphic card settings has a V-Sync option and try to disable it.
The speed is slower with NX853 MP2
I have also just found that if you set your motion display option to +/- 100 motions it goes WAY slower when verifying at a speed of 1 because the system has to keep re-calculating the moves to display.