If your phone does wake up correctly on power button press but it does not wake up from suspend at all on incoming call despite of the signal being heard on the calling side, it means you have to contact support to get the modem’s firmware updated.
Keep in mind that I’m not talking about anything else other than merely waking up on incoming calls/messages. It should wake up from sleep, but actually noticing and reacting to calls in timely manner is not exactly supposed to work reliably yet (although we should get there pretty soon now).