2925 N-plus

We upgraded the firmware on the Draytek 2925 N-plus router to version 3.7.8.1. After this, we seem to be having problems with broadcast traffic from the wireless to the wired LAN. For example, resolving MAC addresses on the wired LAN (arp). If the address is already in the arp cache, communication is fine, but when the arp cache entry expires, communication fails. Also, DHCP is an issue - also broadcast based - with hosts on the wireless network failing to obtain an IP address from the wired DHCP Server. Enabling the DHCP relay on the router fixes the problem, but the relay was not required prior to the upgrade and should not be necessary. The network currently has a single V-LAN.

Has anyone else had similar issues with this router or firmware upgrade?
Any suggestions?