SNMP and FreeBSD - fails every 2 weeks then recovers

Hi,

I am having an issue with SNMP and FreeBSD. Everything is working fine on a daily basis but every two weeks I get an alert SNMP Failed on all my FreeBSD vms (seems to be related only to FreeBSD, others are fine)
2 hours laters SNMP recovers itself. Alert logs below.

Where should I start looking for the cause?

ok	30.09.2019 22:55:45	x.x.68.122	SNMP check FAILED!
ok	30.09.2019 22:55:45	x.x.68.138	SNMP check FAILED!
ok	30.09.2019 22:55:44	x.x.68.42	SNMP check FAILED!
ok	30.09.2019 22:55:44	x.x.68.38	SNMP check FAILED!
ok	30.09.2019 22:55:44	x.x.68.6	SNMP check FAILED!
ok	30.09.2019 22:55:44	x.x.68.26	SNMP check FAILED!
ok	30.09.2019 22:55:43	x.x.68.46	SNMP check FAILED!
ok	30.09.2019 22:55:43	x.x.68.126	SNMP check FAILED!
ok	30.09.2019 22:55:43	x.x.68.206	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.34	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.114	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.78	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.98	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.182	SNMP check FAILED!
ok	30.09.2019 22:55:42	x.x.68.118	SNMP check FAILED!
ok	30.09.2019 22:55:41	x.x.68.30	SNMP check FAILED!
ok	30.09.2019 22:55:41	x.x.68.74	SNMP check FAILED!
alert	30.09.2019 20:45:56	x.x.68.26	SNMP check FAILED!
alert	30.09.2019 20:45:56	x.x.68.138	SNMP check FAILED!
alert	30.09.2019 20:45:56	x.x.68.122	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.118	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.42	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.126	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.206	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.6	SNMP check FAILED!
alert	30.09.2019 20:45:55	x.x.68.38	SNMP check FAILED!
alert	30.09.2019 20:45:54	x.x.68.182	SNMP check FAILED!
alert	30.09.2019 20:45:54	x.x.68.46	SNMP check FAILED!
alert	30.09.2019 20:45:54	x.x.68.114	SNMP check FAILED!
alert	30.09.2019 20:45:53	x.x.68.30	SNMP check FAILED!
alert	30.09.2019 20:45:53	x.x.68.74	SNMP check FAILED!
alert	30.09.2019 20:45:53	x.x.68.98	SNMP check FAILED!
alert	30.09.2019 20:45:53	x.x.68.34	SNMP check FAILED!
alert	30.09.2019 20:45:53	x.x.68.78	SNMP check FAILED!
ok	15.09.2019 22:30:48	x.x.68.122	SNMP check FAILED!
ok	15.09.2019 22:30:48	x.x.68.138	SNMP check FAILED!
ok	15.09.2019 22:30:48	x.x.68.42	SNMP check FAILED!
ok	15.09.2019 22:30:47	x.x.68.38	SNMP check FAILED!
ok	15.09.2019 22:30:47	x.x.68.6	SNMP check FAILED!
ok	15.09.2019 22:30:47	x.x.68.26	SNMP check FAILED!
ok	15.09.2019 22:30:47	x.x.68.46	SNMP check FAILED!
ok	15.09.2019 22:30:47	x.x.68.126	SNMP check FAILED!
ok	15.09.2019 22:30:46	x.x.68.206	SNMP check FAILED!
ok	15.09.2019 22:30:46	x.x.68.34	SNMP check FAILED!
ok	15.09.2019 22:30:46	x.x.68.114	SNMP check FAILED!
ok	15.09.2019 22:30:45	x.x.68.78	SNMP check FAILED!
ok	15.09.2019 22:30:45	x.x.68.98	SNMP check FAILED!
ok	15.09.2019 22:30:44	x.x.68.182	SNMP check FAILED!
ok	15.09.2019 22:30:44	x.x.68.118	SNMP check FAILED!
ok	15.09.2019 22:30:43	x.x.68.30	SNMP check FAILED!
alert	15.09.2019 20:20:55	x.x.68.74	SNMP check FAILED!
alert	15.09.2019 20:20:55	x.x.68.26	SNMP check FAILED!
alert	15.09.2019 20:20:55	x.x.68.138	SNMP check FAILED!
alert	15.09.2019 20:20:55	x.x.68.122	SNMP check FAILED!
alert	15.09.2019 20:20:55	x.x.68.118	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.42	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.126	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.206	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.6	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.38	SNMP check FAILED!
alert	15.09.2019 20:20:54	x.x.68.182	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.46	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.114	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.30	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.74	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.98	SNMP check FAILED!
alert	15.09.2019 20:20:53	x.x.68.34	SNMP check FAILED!

And before that it was 01.09.2019
====================================
Component | Version
--------- | -------
LibreNMS  | 1.56-3-g74724a461
DB Schema | 2019_09_29_114433_change_default_mempool_perc_warn_in_mempools_table (142)
PHP       | 7.2.5-0ubuntu0.18.04.1
MySQL     | 10.1.29-MariaDB-6
RRDTool   | 1.7.0
SNMP      | NET-SNMP 5.7.3
====================================

[OK]    Composer Version: 1.9.0
[OK]    Dependencies up-to-date.
[OK]    Database connection successful
[OK]    Database schema correct
[WARN]  IPv6 is disabled on your server, you will not be able to add IPv6 devices.

In case this helps the first alert was triggered on 2019-08-03 at 10:35. Since then it’s repeating fortnightly.