I had the Same during my Gig two Weeks ago. I Thought it had something to do with the FOH Mixer. I Used a high gain/high volume rig - some van halen of the Free TAF Rigs.
My setup was KPA Main Out to FOH, and Monitor Out to a 100w FR laney floor Wedge in Front of me, Volume on 6.
I recognized that Sound from the Video 100%, a Sharp hiss! Two me it Sounded like feedback gone digitally Bad. 
Probably Out of instinct ( don barzini: don't get started on this 
) I've turned Down the Volume on my LP a Bit, fixed it.
I had the Same during my Gig two Weeks ago. I Thought it had something to do with the FOH Mixer. I Used a high gain/high volume rig - some van halen of the Free TAF Rigs.
My setup was KPA Main Out to FOH, and Monitor Out to a 100w FR laney floor Wedge in Front of me, Volume on 6.
I recognized that Sound from the Video 100%, a Sharp hiss! Two me it Sounded like feedback gone digitally Bad.
What did you turn down to fix it? What is your LP?
What did you turn down to fix it? What is your LP?
Turned down the volume a bit on my Les Paul (has two Burstbuckers). That hiss happened during the first song of the set (neck PU selected for solo), all other chosen rigs for the set are normal stuff with moderate gain & volume.
So far I don't see a problem to be fixed. As I said, it might be that the digital souls of the KPA turned a feedback of the Laney wedge into bad noise. Let's wait, if the Kemper guys come up with some investigative inquiries about the exact circumstances. Maybe I can reproduce the hiss...
Here another one with the same problem ! Is there a solution ?
Did the noise stop when you quit playing, or did you mute the amp? Labrat solved the issue by turning down - that suggests it is a digital representation of mechanical feedback.
What kind of monitors? How loud are you playing?
Are your pickups potted, or unpotted? Can you talk into the pickups when you are turned up this loud?
The modulation effect is likely being driven into oscillation by the feedback. that normally requires a lot of gain, and a lot of volume Do you have a boost programmed into your modulation effect? They usually lessen the chances of feedback, because they make the signal characteristics less regular. Do you get a "squeal" feedback without the modulation effect?
There is a limit to how loud you can play with a high gain rig before it feeds back, especially when facing the speakers (most of us face the speakers when we WANT feedback - LOL) Do vocals come through the same monitor, too? If so, you may be bleeding into the vocal mics.
The only way to know for sure if there is a digital feedback issue or a volume and gain feedback issue, is to contact Kemper, and send them the Rig you are using when you experience the issue. They will likely ask how loud you play, and for your Clean and Distortion Sense settings.
Even it if is a digital feedback issue, it may be a combination of the Rig and physical volume. The Kemper is capable of extreme amounts of gain, and extreme amounts of modulation, delay and reverb regeneration. They have not limited the extreme settings of the effects to prevent feedback.
But, send your rig to Kemper - even though they designed it to be able to do this sort of thing on purpose, they would likely want to rule out any unintended issues.
Are all three of you having this issue with unedited rigs, or just with rigs you have edited?
I had this issue some firmware versions ago. Happened several times with the (otherwise fantastic!) Trainwreck profile from TAF.
It only ever happened to me with a TAF Profile when the Phaser was in Stomp D, and that was many many months ago with an older firmware.
First thing I did was remove the Phaser from Stomp D...don't turn it off, REMOVE it.
I was able to reproduce the hiss several times with the band. We are playing a nightwish cover. It happens going with main out into the PA or just using my active wedge.
My PUs are Gibson burstbuckers. I hope and I believe they are potted.
The rig is called fat Ed from M. Franzkowiak. The clean Sense is 5 and the Distorsion Sense 0.0. Those should be the Factory settings.
Gain at 14:30
Bass at 15:00
Middle at 17:30
Treble at 15:00
Presence at 15:00
Vol at 12:00
Master Vol 2.5
Sfx: comp, eq, dly, rev.
Thanks for Looking into it.
PS: was with older FW 1.6.1
I reported this a couple months ago, and sent an audio sample . Burkhard wrote back and said engineers did duplicate it and would work on a fix in upcoming updates. Once i narrowed it down to the phaser, I experimented with settings. I found the auto feedback settings on the TAF presets are at 60 ... If you bring that setting down to 45 or so, I couldn't make it happen. Bring it back up, and there it is again. For me, it seemed to happen when playing upper register at quick pick speed.
Any event, kemper is aware, but I guess not fixed yet.
@ Jerryratpack: Thank you for letting us know. Yes, since you mentioned it, I observed that also with the upper registers playing a bit faster, well, not really "shredding" 
This is a bug and will be fixed in the next firmware.
You can avoid it now by not turning phaser feedback above 50 %.
+1
Thanks Christoph 
Good to know! Thank you!
This is also happening to me and I noticed this happening when I'm on Trainwreck profile that I bought from Andy. I also noticed that I got a random flashes of LEDs in the Kemper control panel. Those weird things did not appear when I switched to other rigs. It must be bug issue for me.
