Gilwe, if you feel like you could open the keyboard and check all the connections, maybe using (sparcely) a bit of anti-oxidant spray.
Good luck,
Andrea
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.