MPH indicator on display
 

I have a 99 Boxster base. On the display next to the digital speed indicator is "MPH". The MPH indicator flickers. Sometimes it goes out completely, sometimes it is lit as normal, but often it flickers.

I assume a wiring issue, but I am uncertain where to start. Surprisingly, searching these forums turned up nothing. ;) Usually I find all of the answers I need here.

I am having other wiring issues: Horn does not work (Airbag retainer), e-brake switch just went out, and passenger seatbelt is bad, throwing a code whenever used. It must just be getting to that age.

Any ideas or help is greatly appreciated.