Difficulty Setting Push Destination (Attribute 3, Class 40) - Python Library

Hello,

I am working with the Gurux.DLMS Python library to configure a meter and I'm having trouble successfully writing to the send_destination_and_method attribute (attribute 3) of the Push Setup object (Class ID 40, OBIS 0.0.25.9.0.255).

The Problem

When I execute a write command to update the IPv6 destination address, the operation returns a "Success" status from the meter. However, when I immediately read the attribute back, the value has not changed; it remains the old IP address. i have tried
1. def write_push_destination(self, obis_code, new_address):
reader, media = None, None
try:
reader, media = self._connect()
self.log(f"Writing Push Destination for {obis_code} with IP: {new_address}")

# 1. Use the CORRECT object type to ensure the right Class ID (40) is sent.
push_setup_obj = GXDLMSPushSetup(obis_code)

# 2. Manually construct the exact data payload to match the working Kalkitech log.
data = GXByteBuffer()

# The value is a single STRUCTURE, not an array.
data.setUInt8(DataType.STRUCTURE.value) # 0x02
data.setUInt8(3) # 3 elements

# Element 1: Service Type. Enum, value 1, to match the working Kalkitech log.
data.setUInt8(DataType.ENUM.value) # 0x16
data.setUInt8(0) # THE CRITICAL CHANGE IS HERE

# Element 2: Destination Address (OctetString)
dest_bytes = new_address.encode('ascii')
data.setUInt8(DataType.OCTET_STRING.value) # 0x09
_GXCommon.setObjectCount(len(dest_bytes), data) # Helper to write length prefix
# The correct method to append raw bytes to the buffer:
data.set(dest_bytes, 0, len(dest_bytes))

# Element 3: Message Type. Enum, value 0 (A-XDR)
data.setUInt8(DataType.ENUM.value) # 0x16
data.setUInt8(0)

# 3. Set the fully-encoded byte buffer as the value of our PushSetup object.
push_setup_obj.value = data

self.log(f"Writing cleartext hex data for send_destination_and_method: {bytes(data).hex().upper()}")

# 4. Call write with the object and attribute index.
reader.write(push_setup_obj, 3)
self.log(f"Successfully sent write command for push destination.")

finally:
if reader:
try: reader.close()
except Exception: pass
if media and media.isOpen():
try: media.close()
except Exception: pass
self.log(f"Connection for writing push destination closed.")

2. def write_push_destination(self, obis_code, new_address):
reader, media = None, None
try:
reader, media = self._connect()
self.log(f"Writing Push Destination for {obis_code} with IP: {new_address}")
push_setup = GXDLMSPushSetup(obis_code)

destination_struct = [
[1, 1], # Service: [transport_service=1 (TCP), destination_sap=1]
new_address.encode('ascii') # The destination IP as bytes
]

# The 'destinations' property expects a list of these structures.
push_setup.destinations = [destination_struct]

# Write the new value to attribute 3.
reader.write(push_setup, 3)
self.log(f"Successfully sent write command for push destination.")

finally:
if reader:
try: reader.close()
except Exception: pass
if media and media.isOpen():
try: media.close()
except Exception: pass
self.log(f"Connection for writing push destination closed.")