Suddenly a month ago our shop started getting some new orders with customers defined as guest while being in the general group.
These customers do not fall into the NOT LOGGED IN group, in the database the field customer is guest is set to 0 and orders say that they belong in the general group.
The problem is that because of that, their first and last name are missing from the db, as well as their email and of course they don't have a customer ID.
We haven't done any change and these behaviour seems to be completely random. Most of our orders are fine and behave normally...