Popping out of gear

I have a Hurst Pro Matic shifter. The last couple of times out it's been in 1st gear then it shifts right into 2nd without shifting. I checked the cable, it seems fine (I've had them melt thru) do the ratchet shifters wear out after so long and not hold the gear? This ones probably 7 years old with about 40,000 miles on it. I like to shift manually all the time so it gets alot of use. Thanks