DHCP relay communications are being dropped by IPS signature DHCP, how can I restore communication?

[adriangutierrez]

We have been having this problem during this week, every day at the same time the IPS discards the DHCP requests that go through the firewall, attached image.
I would like to know how we can restore the communication, I have already tried to add an exception for that DHCP signature, but it does not work. What we have had to do is restart the firewall to reestablish communication with the DHCP server.
It should be mentioned that all other communications pass the firewall without problem.

any help is appreciated.

Thanks