HR was stuck at around 115bpm, only corrected once I went out to the controls view (pressing the top left button) and back to the activity. Hope they get a fix soon.
And here are 2 runs at my local park run, the one is where I saw it was low and went out and back for it to correct and the second one where I did not see it and it stayed low for the whole run.
updated to the latest beta 18.12. not listening to music and not having any headphones connected and again I had to exit to the controls menu for it to correct. so still no improvement.
Updated to 19.4Beta and still the issue persist. Watch recorded my HR lower than it actually was, then went lower still before correcting. No music or headphones or phone connected.