Guests would hang shortly after starting and mainly after a GUI login. I.e. Desktop shows and then Guest hangs.
VB Windows process would go to ~35% Utilization for each guest.
Vbox Log indicated maybe an audio issue:
00:00:31.659479 GUI: UIMachineViewNormal::adjustGuestScreenSize: Adjust guest-screen size if necessary
00:00:31.659501 GUI: UISession::sltAdditionsChange: GA state change event came, notifying listeners
00:00:31.659504 GUI: UIMachineLogicNormal::sltCheckForRequestedVisualStateType: Requested-state=0, Machine-state=5
00:00:32.727202 Audio: Warning: Scheduling hint of stream '[WasAPI] Output:0' is bigger (140703128616965ms) than used period size (0ms)
00:00:32.939314 Audio: Warning: Scheduling hint of stream '[WasAPI] Line-In:0' is bigger (140703128616970ms) than used period size (0ms)
00:00:33.344308 GUI: Releasing mouse on capabilities lost
00:00:54.304350 GUI: Releasing mouse on capabilities lost
00:01:01.565870 VMMDev: vmmDevHeartbeatFlatlinedTimer: Guest seems to be unresponsive. Last heartbeat received 4 seconds ago
00:01:08.704426 GUI: Releasing mouse on focus out
00:01:08.704453 GUI: Releasing keyboard on focus out
00:01:08.704832 GUI: Machine-view #0 unfocused, reason=4
00:01:23.911386 GUI: Capturing keyboard on focus in
00:01:23.911447 GUI: Machine-view #0 focused, reason=4
Disabling Audio in the Guest seems to stop the issue. Luckily I don't need audio for my server labs
