Instability with ION USB turntable

I am using the current version of Audacity with Windows 7 to record vinyls using an IONS turntable. Everything works fine but every so often for no apparent reason the system goes unstable and gets stuck in an oscillation/humming mode. Can anyone advise what might be the problem?

If you get the same problem from the analog outputs you’ll know it’s the turntable itself. (You can plug the line-level outputs into your stereo, your TV, or powered computer speakers, etc.)