I walk on the treadmill while lifting and carrying dumbbells. My Venu2 was monitoring my HR accurately for quite some time. In the last two weeks, it stopped monitoring my HR accurately, showing 76bpm +\-. This is happening on my Sole 63 and others.

Loss of HR monitoring when walking on treadmills and lifting / carrying dumbbells. I have been walking with dumbbells for a few months and my Venu2 was accurately monitoring my HR.  Recently, the last 2-3 weeks, it has not been recording my HR but measuring a constant value of 76bpm.  Are the weights interfering? I do not wear a chest monitor.