(Austin, TX USA)
My 8700SST is about 25 years old and gets daily use in the cardio mode.
My problem is that the sampling rate is too slow, about every 15 seconds, so my heart rate is allowed to go higher than the range, then it overcorrects so the heart rate is below the zone, and it doesn't really stabilize in the 40 minutes in-range I use.
The sampling rate needs to be every 5 seconds or so to prevent this problem. I am 74 years old, use 120 as my target heart rate, maximum 3.5 degrees incline and maximum 3.5 mph.
Is there a software update that will fix this? Everything else is fine.