VST via USB sounds terrible one the X (buffer underrun?)

[BlackForest]

I am having the following issue on one of my two Kronos:

Setup: a Win10 laptop with Kontakt 7, connected to the USB port.
Driver is ASIO4All.

Kronos 2 works fine.
Kronos X sounds terrible, sounds like buffer underrun. Never mind what I try to change in the ASIO4ALL buffer sizes and sampling 44/48 kHz settings, it won't work.
It is not clipping the sound, also the other inputs (SPDIF,.. are all off).

The only difference is the motherboard and the USB cable. It is NOT any electrical interference noise as it only happens when I try to play the VST.
I am not even sure if this could feed into a USB connection anyway.

Can it be that the X's USB port/MB doesn't cope with this setup, or is too old?

Have you had similar experiences?

I wanted to avoid using a separate A/D converter or the audio card inside the laptop.

[voip]

What does the laptop internal audio device output sound like, when playing the VST using the Kronos X? It might help to narrow down the problem.

I've encountered a case of distorted audio issues with Omniphere on a laptop, using a laptop internal audio device. The laptop battery had pretty much had it, which might be causing unstable internal supply voltages, as the laptop power supply tries to charge it. Sourcing a replacement battery has been a problem, so the observation is not conclusive.

Whilst a failing battery might not be the issue in your case, there could be some sort of ground loop that might be affecting the laptop's internal supply rails. Rearranging the mains supply and earthing arrangements might make a difference.
.

[BlackForest]

I haven't used the internal sound system (yet). But as said, it works with my KRonos 2 well.

I could try to record it, good idea, however am not close to my X now. THe laptop was on battery, and it lasts "ok", about 2-3 hrs.
But thanks for trying to help.

[BlackForest]

Ok, I tried, so the laptop with its own Realtek Audio, via the ASIO4ALL, works well.
The Kronos was not connected at all.
The latop is running on battery, an IBM ThinkPadT460s.