Since the 7.60 upgrade my 5x keeps reversing the run/walk. I do a 4/1 and it keeps reversing it to 1/4 (run/walk). It does it in all run modes. (Run, trail run, treadmill...)
Once I reprogram it (just before a run) it holds it for that run. Once it syncs, either over the air or hard wire - the reverse happens.