Linux agents specifically, but also some Windows agents connect to the same CP regardless of what the Automation Engine returns for CP ranking. Example:
20210528/180129.923 - U02000354 CP Server 'AUT1235#CP003' reports ranking '1'.
Release : 12.3
Component : AUTOMATION ENGINE
This was caused by older agents attempting to connect to the automation engine
This is resolved by updating the agents which were on older major versions (ie. 12.0) than the major version of the automation engine (ie. 12.3). Updating the agents allowed them to load balance correctly.