Mild weirdness, tough to repeat:
webCoRE --> Settings --> Available devices and contacts --> Available devices --> Which sensors
Select a sensor
Done --> red “There was an error…”
Or, select sensor, go back, click “which sensors” again, and the sensor isn’t selected.
Might also behave similarly with actuators.
Works after Done --> Done --> Done --> Done --> green “Successfully updated webCoRE”, but sometimes I have had to do it twice.