DHCPv6 not working?

Question

DHCP

There is such a scheme. There are 2 DHCPv6 KEA servers. The problem is that from 1 DHCPv6 addresses are not distributed, from the second everything is normal. The settings are the same. Lupbeki responds all the rules.
The dump is something like this
16:56:42.627719 IP6 (flowlabel 0x5bc41, hlim 64, next-header ICMPv6 (58) payload length: 214) dhcp > 2001:X:X:X::1 [icmp6 sum ok] ICMP6, destination unreachable, unreachable prohibited dhcp
Firewall, ACL nothing.