Better Pedometer - HELP NEEDED!

I have had both bangles on 2v11.53 for a few hours now (mostly sitting at desk) and the step counters are still different.
b77 has counted 167 steps, while b87 counted 667. So a bit closer together than before.

jeffmers test harness and stepcount.c yielded:

X_STEPS = 6, RAW_THRESHOLD = 15
File, Expected, Simulated, Diff, %, (Original)
halemmerich-walking-2-b77-2v11.csv, 150, 79, -71, 52.67 %, (156)
halemmerich-walking-2-b87-2v11.csv, 150, 89, -61, 59.33 %, (151)
halemmerich-stationary-1-b77-2v11.csv, 0, 0, 0, 0.00 %, (1)
halemmerich-stationary-1-b87-2v11.csv, 0, 0, 0, 0.00 %, (10)

I have had play with the RAW_THRESHOLD and got down to 7 before the results were reasonable.

X_STEPS = 6, RAW_THRESHOLD = 7
File, Expected, Simulated, Diff, %, (Original)
halemmerich-walking-2-b77-2v11.csv, 150, 150, 0, 100.00 %, (156)
halemmerich-walking-2-b87-2v11.csv, 150, 143, -7, 95.33 %, (151)
halemmerich-stationary-1-b77-2v11.csv, 0, 0, 0, 0.00 %, (1)
halemmerich-stationary-1-b87-2v11.csv, 0, 12, 12, 0.00 %, (10)

I also tried walking 150 steps. b77 counted 80 steps and b87 counted 103.