Hi @sven - Sorry to hear that you had stability issues with the JS220 and Joulescope UI. Thank you for reporting this issue, which I have definitely not seen. The log snippet does seem to indicate the JS220 either reset on its own or was reset by the host.
The voltage input is extremely high impedance by design. It tends to drift towards the JS220’s power rails due to the opamp input bias current. This gives strange “noise” measurements when left open, but it should not cause the JS220 to reset.
What host OS are you using?
Would you mind trying your JS220 with the voltage open using the Joulescope UI 1.0.x alpha? Does the same error occur?