I can create a query, such as
GET /rest/v11_4/Employees HTTP/1.1
{"offset": 4, "max_num": 1}
GET /rest/v11_4/Employees HTTP/1.1
{"offset": 5, "max_num": 1}
and up to
GET /rest/v11_4/Employees HTTP/1.1
{"offset": 17, "max_num": 1}
They return the same data each time, same id, same everything. It was first seen where the last record of a batch of 20 was the same as the first one of the next 20, but the above with num_row=1 shows its clearly.
Oddly, If i add a field_list to the query, I don;t see the problem, and I get the expected results with each id only appearing once.