Change the sampling rate for data collection to 25 or 50 samples / second.
When more than one probe is plugged into an interface such as a LabQuest, LabQuest2, or LabQuest Mini, the data-collection software will automatically select the slowest default sampling rate of the sensors in use.
The default sampling rate for a temperature probe is 2 samples / second. The default sampling rate for the Hand-Grip Heart Rate Monitor (HGH-BTA) and Exercise Heart Rate Monitor (EHR-BTA) is 25 samples / seconds.
2 samples / second is much too slow for the Heart Rate Monitor to work properly.
If you change the default sampling rate to 25 or 50 samples / second you will get good data from both sensors.