May I ask the purpose of this firewall filter (not firewall)? Without the filter DHCP/DHCP-Relay works, that is permit happens, which seems to be the action you want anyway, yes?
I can only guess that the firewall filter action causes the packet to be forwarded by PFE and not forwarded to RE (required for relay I believe?). Are you seeing the filter being hit?
I would think some standard troubleshooting stuff could be done as a first step,but I still wonder what the reason for this FF in the first place is.
Good luck.