Can two Radar motion sensor, running next to each other, result a false detection?
A CDM324 module is a very simple device.

There isn't even a crystal or any other component on the board (see here) which takes care that the 24 GHz frequency is accurate. So the frequency will not be accurate. That means that the module will need to work over a wide frequency range. That also means that any other device within range operating at 24 GHz or a frequency close to 24 GHz can disturb this device.

Your only chance is that two modules are using such a significantly different frequency (like 23.5 GHz and 24.5 GHz) that the frequency difference is so large that this cannot be picked up by the boards.

But there is no guarantee that two (randomly selected) modules will have such significantly different frequencies that this will work.

The safest option is to only use one board at any moment (time-share).