I contemplated buying a Kone for a 1x12 cab I have. I just can't get to feel like an amp. No sustain, dead notes, weird high E string sounds, lot of stuff. It sounds great on many things, really weird on others. Tired of wrestling with it,
No sustain, dead notes, weird sounds from you high E?
Sounds like the Kemper is showing you the sound of your actual guitar, and your prior rigs may have masked it, especially if you play with gobs of distortion.
The symptoms you describe are guitar issues, not amp issue traditionally.