If you're going to use Multicorder for vMix calls, if you get multi-file recordings, here's how you use them afterwards:

You need to import the XML file to a video editor as a Final Cut Pro project.

This will then lay out the video files in the correct time order.

However, when the video drops out, you'll have a black screen. in vMix, when the call drops out temporarily, it holds the last shot of the caller as a freeze-frame. It won't do that in a video editor.

So what you'll need to do is drop a still of the final frame of each file in the gap to cover the blips.

Then render it all out as a single file and go and remix the video(s).

As for the audio issue - you can either check the latency on each caller while you're recording, or shift the audio by a few frames in the editor. Setting audio latency on the initial recording would be the way to go.

If you're talking about Multicorder files having audio out of sync with the video - yes, I've seen that too. Haven't seen it reported as a bug on the forums, been meaning to post it myself.

The solution to this - again - is to re-render the video. For some reason, loading the Multicorder file into vMix is where the de-synced audio occurs. Doesn't manifest in Windows Media Player, or within Adobe Premiere.