It looks like recently there are more and more problems connecting with the SAP V3 module. My current theory is that this is caused by a bug in recent Android Bluetooth software, since it often happens after system updates or with recent Android versions. Maybe it's a bug in the new Broadcom Open Source Bluetooth stack, which is used by more and more phones.
Technically it looks like a request to the Service Discovery Protocol (SDP) does not give the expected answer and the SAP module simply quits. This is very basic and low-level Bluetooth stuff which I don't fully understand. It doesn't seem to be a problem with rSAP - the SDP request for rSAP happens directly before the failing request and looks fine.
So either someone will have to fix the Bluetooth code in Android, or Mercedes will have to change the SDP request or handle the unexpected SDP answer more gracefully.