Howdy,
I'm a fairly happy owner of a F6 pro - we all have our little niggles with the device but for the most part, mine works nicely.
However, my training is focused around low HR workouts in a roughly 80:20 ratio.. 80% low and 20% high intensity. This type of workout scheme appears to confuse the built in training metrics and even though my own fitness is improving, the watch is nearly always reporting unproductive or detraining.
I run on average 5-6 times a week with 3x 10-15km slow low HR runs, a long 15-25km slow low HR run and 1 or 2 high intensity runs off around 10km. I also do about 50km of biking, either road or MTB.
Its got to the point now that I pretty much ignore all the metrics coming off the watch for training status and solely rely on the watch for HR and GPS data only.
I seem to be one of the lucky ones and get accurate HR readings from my watch, I'm an EMT by profession and have tested resting and post workout HR with our medical equipment and the watch is pretty accurate.
Anyone else in the same boat for training metric issues?