[FROG] IS-IS Error

Hi all. I'm almost there getting IS-IS to work without issue. I'm now faced with the following error log: 2020/04/17 10:02:01 ISIS: IS-IS bpf: could not transmit packet on em0: Input/output error 2020/04/17 10:02:01 ISIS: [EC 67108865] ISIS-Snp (1): Send L2 PSNP on em0 failed This repeats every second. Anyone know what this could be? Systems is FreeBSD-12.1-RELEASE-p3. Despite the error, IS-IS is running and routing is good, talking to a Cisco IOS XE implementation on the other side. So the error is throwing me off. Mark.