Hi Scuz,
That's probably because there's too much work for your AUs to handle in the configured buffer size, by default this is 512 samples, meaning about 11ms at 44.1kHz. EigenD has a System Usage Meter that you can access from the Window menu. When that's going into the red, you'll start getting drop outs since 11ms have passed and some AUs might not have calculated the sound yet.
There are several ways to improve this:
* you can increase the buffer size in the audio settings, but you'll also increase latency, it gives the plugins more time to process
* some plugins have different "fidelity" or "quality" settings, reduce those so that it has less to calculate
* some plugins allow you to set a maximum of active voices, using less of those will free up processing power for the most current ones
* some plugins (like U-he Diva) are incredibly resource hungry, they might sound awesome but really can bring a machine to its knees, maybe look around for alternatives that are similar and less hungry
* there's a decimation setting in the global configuration for each audio unit that EigenD hosts, increasing that, reduces the amount of MIDI messages that will be sent to the plugin (not the host automation parameters). This might help but I've rarely seen it be an issue, it's mostly used for slower physical MIDI connections
* free up resources on your computer by quitting all other software, turn off Wi-Fi, disconnect it from the internet and only use EigenD. I personally have a dedicated MacOSX partition for that so that nothing else runs inadvertently.
* make sure that audio unit agents that aren't in use are automatically but into idle by EigenD by turning 'Tail Time Enable' on and giving it a reasonable interval.
* as a final resort, upgrading your computer to a faster CPU will allow your plugins to calculate faster and possibly get done in time for the buffer size
Hope this helps,
Geert