You are not alone on this. My MC21 went through a phase where the tachometer would not work when first starting up in neutral. Once I put it into gear it would work normally. The temp gauge was also slow to register.

The problem went away after I started riding the bike more frequently so I can't give you a specific fix for the problem. I would be interested to hear from the more mechanically minded to understand what would cause this. Whether it's just loose wiring or whether the electrical system has any impact?