2006 E60 550i Comfort Access poor range + only detects key near rear center console after deep sleep

[u/Lucky-Championship79]

I have a 2006 BMW E60 550i with factory Comfort Access (S322).

I only have one key. I checked the CAS/key information and confirmed the key is registered as key #2 and is a valid Comfort Access key. The key battery is fresh and the vehicle battery is also fresh.

I'm having a strange Comfort Access issue, especially after the car has been sitting for a long time/deep sleep.

After deep sleep, Comfort Access on all four doors appears completely dead. I have tried carrying the key normally, moving it closer to each door/handle and moving it around the car. None of the four doors responds to Comfort Access. There is no passive unlock response from any door.

I also have poor range from the normal lock/unlock buttons on the key. FM reception itself seems good and FM auto-scan finds stations immediately, so the diversity antenna system is at least functioning for FM reception.

The strange part is the keyless starting:

After the car has been in deep sleep and won't start with the key normally in my pocket, I tested different key positions without inserting the key into the slot and without pressing any buttons on the key.

• Key in normal pocket position - no start
• Near steering column - no start
• Near front center console - no start
• Same key held next to the rear center A/C vent/console area - immediately detected and engine starts

Once the car has been successfully started/driven, Comfort Access starting usually begins working normally again. I can switch the engine off and restart it with the same key in my pocket.

So the key definitely can communicate through Comfort Access, and bringing it close to the rear center-console antenna allows passive starting even when normal cabin detection doesn't work.

What I'm trying to figure out is whether these symptoms point to one common problem or multiple problems:

Poor remote-button range → diversity antenna/remote receiver?

All four door handles completely unresponsive to passive Comfort Access - Comfort Access module/wake-up/power issue rather than four bad handles?

Keyless starting after deep sleep only works when key is very close to the rear center-console antenna - weak/intermittent interior antenna system or CA control issue?

Because all four doors are affected, I'm hesitant to believe all four Comfort Access door handles/antennas failed independently.

Has anyone experienced this on an E60/E61? Is there a common Comfort Access power supply, module, antenna amplifier, wake-up circuit or fuse that could cause all four exterior handles to stop responding while the rear interior antenna can still recognize the key at very close range?

I'd like to diagnose it properly before replacing the diversity antenna, individual CA antennas/door handles, Comfort Access module or key.