CyanView Products provide remote CCU operations via an internet connection to any cameras they support. (Our use case is with a Sony XD PDWF800) They usually work well!
Their version of a Camera Control Unit (CCU) is called an RCP.

The RCP if connected to the same network as the vMix PC can connect straight to the local vMix server to receive input,output and tally information to send to cameras remotely via in built configuration in their local management browser.

Error experienced - if you opt to use 'Outputs' in CyanView Manager and connect an output to a source in vMix, that source will be triggered as an overlay whenever you use transitions or other sources.
For some reason, it linked specifically to the Instant Replay system in vMix. Cutting to a replay would trigger Cam 2 (Source 2) on overlay 1. But every now and then it would overlay a source with no apparent rhyme or reason.

I have spent days searching for vMix errors, I thought it was a corrupted Instant Replay Session in vMix or a misfiring vMix trigger.

But at long last - I have found the issue to come from the CyanView RCP.

Now that I have disabled the use of all output settings between the CyanView RCP and vMix, leaving only tally info, it seems to be behaving.

Hope this may help anyone else integrating vMix with any CyanView products.