Today I had a issue with a remote site, RB3011 updated to 6.43.7 and it stoped working. After many checks we discovered that after the update a dhcp-client is automatically setup at port ether1, and on our case this port is connected to a PPPoE bridged router and serves also IP (but don't get out to internet). We had this "new" dhcp-client distance 1 and pppoe client also distance 1, and the trafica wasn't getting out, until we went to the site and after debugging removed this new dhcp-client.
I've replicated it with a rb750gr3 and the same issue,, after the firmware update there is a dhcp-client on port ether1.
Please remove this auto-setup dhcp-client, it can break many updated sites!!!