The default heart rate in emulator is set to 100 bpm. When u try to change it on anything different- result value is drops to 0. And from than u cant set any HR until delete this emu instance and get new.
here is video of behaviour: https://youtu.be/jOe_c0coNAw
Os: Windows 10
Emulator manager ver 2.6.10
Emulator control panel ver 2.2.6
Emulator for 4.0 sdk ver 3.7 package ver 220.127.116.11