I’d advise asking Elektron for a recommendation. But given the focus is on switches I would suggest a product like the one I used to breathe life into ageing Nord switches and regular pots (categorically not encoder type knobs)
As always, do due diligence. But a dedicated product to flush out residue could give them a few more years. Get advice on general board cleaning from Elektron if there’s residue elsewhere that’s less obvious that may cause issues if uncleaned. Product is linked in link.