I tightened the walking belt on my 2500 R to the specifications in the manual (3" - 4" height when lifting belt at sides). This corrected the slippage, but now the speed indicator will show the initial speed (say 6.0...) but when it changes back to the speed screen from the 'pace' screen it shows 0.0. It will remain like that as it toggles back and forth from speed to pace and back. Any ideas?