Hi Sandra,
R3AS does not just do initial load. It also does delta load. If you run SM30 on table CRMRFCPAR in the ERP system, you can find the settings related to that (load type). Check your settings in there to make sure that delta changes are going through.
It is not clear whether your test is based on any existing material or not. So, one way to verify whether the alternative UoM is coming through at all is to create a new material in the ERP system with alternative UoMs. If it does come through, then may be it is the delta replication that is not working and this can be due to the settings in your system.
Regards
SF