Sluggish Rev Counter

Hello All

my rev counter has become very sluggish to react when increasing or decreasing the revs. When it finally catches up it still appears to indicate reasonably accurately. 

I have tested the rev counter off the bike with a drill and spare cable and it acts just the same. It’s had very little use in its life and is not showing signs of corrosion. 

I guess it may need some specialist attention noting how tricky it must be to remove the crimped on bezel. 

Any thoughts or info about where I could get it fixed would be appreciated. 

Alternative would be to find a replacement either new 😆 or a very good used one I guess. 

thanks

JR