ReinardSynth #12 Roland D50 Repair: sound only at key release?

This time a Roland D50: came to me with some weird behaviours: locked up when pressing some specific front panel buttons, sound only when releasing a key... hmmm... Anyways, got it in full working order again; and learned something as well. Do you want to know what LEGO has to do with it? watch until the end. Incidental music: Me and my Yamaha Montage, having some fun with Amber Mark's "Mixer". Tools used: Steinberg UR22mkII + Audio technica 2020 for voiceover, Sony ZV-e10 as video camera, Manfrotto Magic Arm Editing: iMovie (Easy bits) + Davinci Resolve (difficult bits)