PDP Problems with HL7692

We have migrated from a 3G modem HL8548 chip, to the 4G HL7692.
However, attempting to make a PPP connection always returned zero’s and failed.

We have since managed to get the 4G connection working by setting the PDP context to 2, i.e.

And dialling:

Here is the link on another forum that advises the same:

Can anyone tell me why this works?
Is this is correct?

According to the link above, PDP context 1 is reserved for retrieving an IP address and using it results in a conflict. Is this true? Does this refer to the Default EPS Bearer that is established when attaching to the network?

Why do we have to create another PDP context/Bearer for this to work?
Could this solution cause any other problems?