If your lights do not fade smoothly under DMXIS control (and you are using a Windows computer) this may be caused by incorrect audio driver settings.
In the DMXIS standalone, open File > Audio/MIDI Settings and select an audio driver with a low latency, ideally less than 30ms.
If you get the problem with the DMXIS plugin in an audio host, try reducing the audio buffer size in the host program to 40ms or lower.
Background: DMXIS uses the incoming audio stream for synchronisation. If the audio is being passed to DMXIS in very large buffers (i.e. if the audio latency is more than 40ms) this will slow down the DMX refresh rate, which in turn can cause flickering lights. It can also cause your audio to run out of sync with the lighting.