I got a garmin 38 as a gift back in 1998 or 99 and it was un-reliable as he!!
The govt purposely made the signal not be very accurate for security measures. Used to the signal would get you within like a 30-50' range. Now it's accurate to 3-10' or something like that.
No that was not the issue, it was and is that it's antenna wasn't that sensitive.
I can put both gpss side by side and the old 38 will show 1 or 2 satellites (need 3 for 2d and 4 for 3d navigation) and the 60 show 8 or 10 satellites. The owners manual for the old 38 explained the built in inaccuracies that the US government put in the signal.
I have thought of buying a serial port cable for the 38 to see if I could do a firmware update on it and if it would make a difference