Port mirroring on HP 1820-8G (J9979A)

I have a HP 1820-8G switch [German website] with the latest J9979A firmware [HP] at the day of writing. I'm trying to set up port mirroring via the web admin UI.

Whenever I add a source and press the Apply button, the switch hangs, i.e. the web UI does not respond and the switch caot be pinged any more. The switch itself works, i.e. my PC can still coect to websites.

Is there a fix or workaround possible except pressing the hardware reset button?

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