Easiest fix is replacing the OBC. Its as easy as popping the old one out and the new one in. Of course, you'll need to disconnect and connect the connectors in the back. You can actually reach in from the top of the sunglasses holder and push it out. I use a small flat head and carefully pry out the left side while pushing it out from underneath. Just grab the damn thing and pull it out, they're are no retainer screws.
The 7 button and 11 button obc's are interchangeable. The 11 button however is plagued with dead pixel issues. It is easiest of course to swap with a similar one to what you already have. If you have an 11, the 18 button will fit but require a lot of wiring for all functions to be available.
A new OBC is available on eBay for cheap.