I don't think I have driven in really heavy rain yet.
It does say in the manual that heavy rain is one of the system limits. I guess the rain would effect the camera.

At first glance Dynamic Light Assist does not appear to be in the Owner's Manual. It is not in the index. I found it under Main Beam Control p107.
System Limits The system has to be manually switched off under the following conditions, as it is not switched off by the main beam assist in time or not at all:
- In poorly lit streets where there are highly reflective signs.
- There are other road users with insufficient lighting facilities, such as pedestrians, cyclists.
- In tight bends, brows of hills or depressions in the land or half-hidden oncoming traffic.
- With oncoming traffic on streets with central barrier where the driver can clearly see over the central barrier e.g. truck drivers.
- In fog, snow or
heavy rain.
- In dusty or sandy areas.

- ... damaged...
- ... dirty...
- ... broken...
WARNING- Do not let the extra convenience afforded by main beam control tempt you into taking any risks when driving - this can cause accidents. The system is not a substitute for the full concentration of the driver.
- Always check the lights yourself and adjust them to the prevailing conditions for lights, vision and road traffic.
- The main beam control may not be able to recognise all driving situations correctly and may not work properly in certain situations.
- blah, blah... dirty, covered, damaged...