"clink" sound on higher notes


After playing saxophone with the VL3, i use it now with the Blues Harmonica.
Sometimes when I play a very high note on the harp, the sound from the VL3 begins to "clink" oder "stutter". 
I uploded a file to demonstrate.
Then it don't stop, even if a change the preset. The only way to stop that sound is to shut down the VL3 and start it again.

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