audio track stops sending to Stereo Out in Cabase 8 Pro

Cubase
,
1

Several times a previously functioning audio track (recorded voice or guitar) stops sending to the Stereo Output. I can put on a Send to an FX master track and it sends to that just fine (say a master reverb plug). It simply stops sending actual channel output. I can change the output from Stereo to some other buss and it doesn’t make any difference. Yet the meters bounce around normally when the song is playing.
There are no plugins on the tracks and they previously had worked for months.
It doesn’t matter if I solo or not.
I haven’t found any pattern to it other than it seems to have happend when trying to add a plugin to the track while the song was actually playing. However, I have done this all the time so am not sure.

I have done the usual due deligence (resetting Audio settings, closing, rebooting, etc.)
The only workaround I have found is creating a new audio track and moving the wav file over to it.

Anyone know either how to prevent this from happening, or at least how to fix it when it does?

I have a 64 Gig PC running an Intel 3930K (hex core) overclocked to 4.5 GHz. It runs great.
All my projects are 96KHz and before Cubase 8 Pro this had never happened.

Any/all help/comments are greatly appreciated!

2

Let me add that I have a Lynx Aurora 16 for my AD/DA, and ASIO Guard is OFF.
I have tried different buffer sizes (after this has hapened) and not been able to get the audio tracks to start sending to the channel output (stereo out, or otherwise). I can see the individual track meter working, and if I use a SEND to route the channel to an effect buss it works, and I can see the panning working on both the individual channel meter as well as on the effect buss channel meters - but the meters on the main stereo output show nothing.

I am not able to reproduce this hence there are no repro steps.
However, several projects that this has happened on have from between 20 and 40 channels, some of which are MIDI/VST channels. NOTE: This has only happend on actual recorded audio channels - it has not happened on a MIDI/VST channel…yet.

Any help would be greatly appreciated!