I seem to have a very strange problem with DHCP Server.

RB750GL v5.11
DHCP Server on VLAN interface having 1 pool of 99 IP addresses.

It was working fine until all of a sudden PC's were not accepting any IPs assigned to them with errors:

dhcp(LAN) client XX:XX:XX:XX:XX:XX declines IP address 172.16.10.x

I know that probably a power cycle reset will fix the problem, however this is a live system and connot reboot it easily.

Did try to investigate, if the offered IP is not duplicate? Maybe some client has fixed address, and the MK offer the same. I have experience, that not all DHCP servers check the address before lease. Cisco do the check, Juniper has no problem to deliver occupied address. I don't know how the mikrotik works.

Please see my post here: viewtopic.php?f=7&t=96472&p=699200#p699200