I send it MIDI CC #64 value 127/0 - I've tried various MIDI channels (Panel and Instrument). Also tried enabling/disabling the sustain of instruments itself but no avail.
Same thing works fine (and always did) for my NL2x.
Curiously enough CC64 is not mentioned anywhere in the MIDI CC list in the manual. However it is mentioned in the beginning of chapter 14:
• If you have a sustain pedal connected to the SUSTAIN PEDAL INPUT, this is transmitted and
received as Controller 64 (Sustain Pedal).
-Nord Stage EX manual
I have no idea what's going on