[FROG] FreeBSD 12.1 / FRR 7.4, error inserting v6 routes into zebra/kernel

Hi, I'm maintaining the FRR plugin for OPNsense Firewall, currently based on FreeBSD/HardenedBSD 12.1 with FRR 7.4. I received a report from a user that a peering via v6 the bgpd successfully receives the v6 routes which are also displayed in sh bgp ipv6, but they wont get into the routing table and in frr.log there's: kernel_rtm: X:X:X:X rtm_write() unexpectedly returned -2 for command RTM_ADD Bit more details and screenshots are also here available: https://twitter.com/TallWireless/status/1309489192502734850