Hi !
Before 14.2R7.5 there were a lot of bugs and problems in the EVPN code and also some visible and invisible behaviour changes from version to version.
According to personal experience and experiences from two bigger comapnies in Germany the R7.5 is the first and only version stable and recommended for EVPN
Therefore I assume that you trap into such behaviour change and I think you have to upgrade all MXes and maybe also the EX9200 junos to have the same features ( but I have never used that EX9200 one for EVPN).
But I know that this is somewhat risky in a production environment.
With best regards
Alexander Marhold
JNCIP-DC