VST instruments sound, loopback issue in Cubase 8.5 Pro

Load an instrument track, pick a preset - Steinberg or third party synth, playing a chord in Chordpad. Sometimes is working fine, but in most of cases the sound freeze in a loopback after a time playing normally and it cannot stop before i change the preset, or reload the plugin. No Sends or Inserts are active, No delays or other effects in the plugin. Sometimes the bug appear when i play a single note, not using Chordpad, but most often with Chordpad.

Program: Cubase 8.5 Pro and Artist 8.5
System: win7-64 pro, Intel I5 (4460) 16GB Ram, 1TB HDD SATA
Soundcard: Steinberg UR44 set at 384 or 256 samples buffer.
Keyboard: M-audio Radium 49