Mine was acting up last year (old C80). Ebay has a number of repair services listed. I was going to use this one: https://www.ebay.com/itm/185388514828 100% positive feedback over 317 buyers. I had the very common display ribbon problem, so my display would spontaneously flip out and I'd get just jumbled horizontal lines. I ended up fixing it myself though, just cleaned the ribbon and re-seated it, so I never did actually use that service. Different unit and problem than yours obviously, but that's an option I found at the time. (Couldn't find anybody local or nearby, even Minneapolis.)
Greetings,
Mr. S. Got this from another site. Know NOTHING about the company except the OP there (other site) was happy with the repair of his Furino Nav Net screen. Nor do I know if they service anything other than Furino BUT they may be able to refer you to a similar Raymarine repair company. Hyde Marine Instrumentation - Hyde Marine Instrumentation
Buy an RMK-9 or 10 remote keypad. If touchscreen goes wonky (as mine does randomly) use the keypad. Simple, easy fix and should cost a lot less than out of warranty repairs.