I've had zero issues on 16.16.
Anything interesting in the MX event log?
Anything interesting in the MS event log?
What does the MS local status page say when it is not working?
If you plug a notebook into the same VLAN can it get a DHCP address?
Does the MX DHCP scope show it has plenty of spare capacity?
Does a packet capture on the MX for DHCP packets show anything interesting?