Hello,
we have 2 routers (mikrotik). This routers are connected to main switch, we are using vlans. DHCP server is mikrotik too, lease is with server “all”.
When We enable DHCP Relay for each vlan on each router, client will not bound - on server is offered for one secdond, then waiting.
When We enable only one DHCP relay on one router, weverything is fine.
Where is the problem ? 
Thank you