An occasional switching click is different from repeated chatter or a fault.
Relay-equipped thermostats can make an audible click when their contacts switch the heating circuit on or off. Resideo lists relay switching for the TH115-AF-GA and TH114-AF-GB models.
An occasional click that coincides with normal heating control is expected relay behavior. It is not a measurement of current and does not, by itself, prove that the heater is working.
Repeated rapid clicking, a display that continually restarts, failure to control the heat, a burning smell or repeated protective-device trips need diagnosis. Switch off the affected circuit if there are signs of damage or a recurring electrical fault, and have a qualified electrician check the exact control and installation. Do not bypass its relay or ground-fault protection.
Sources: TH115-AF-GA specifications and TH114-AF-GB specifications (Switch Type: Relay).