It sometimes happens that after installing the multi-zone thermostat, the radiator makes a ticking or bubbling sound. This is often caused by the fact that the heating system has been emptied of water and has been refilled. You can remedy this by venting and topping up the system again after installation.
If you keep hearing a ticking sound in the radiator, the following may be the case. This happens in many cases when the radiator is connected the wrong way around. You will not notice this if no smart radiator knob is installed. Only when you make it smart does it become apparent. If the radiator is connected the wrong way around, the valve is connected to the return pipe and the supply pipe enters the radiator where the valve is not.
The result is that the water flows back through the valve. The valve has a rubber that will flap if it is moved the wrong way. Most likely, this is the sound you hear.
To check this, heat the radiator and feel which pipe heats up. If this is the pipe that is not near the valve, then your radiator is connected the wrong way round.
Unfortunately, we cannot solve this problem. If you experience this problem, it is advisable to contact a plumber; they can switch the radiator for you.