Hi,
I beilive you are hitting the below PR 916522 :
https://prsearch.juniper.net/InfoCenter/index?page=prcontent&id=PR916522
The bridge address shown here is the chassis mac address of it own. This MAC address belongs to the chassis itself. It is an informational messages and will not impact any service.
You may plan to upgrade any of the resolved version to get rid of this.
Regards,
Ajo Thomas