Strange spine behavior

[alerm]

Strange spine behavior or maybe DB or host (CentOS release 6.6). One or two times per day (at 3:00 am and 5:00 am) some graphs have been broken. In debug mode in log i see that spine starts at 3:00 check all hosts (about 8-15sec) and then nothing... after that spine start at 3:05 check all nodes and show stats for 2 spine process!

# spine started at 5:00
07/24/2015 05:00:01 AM - POLLER: Poller[0] NOTE: Poller Int: '300', Cron Int: '300', Time Since Last: '300', Max Runtime '298', Poller Runs: '1'
07/24/2015 05:00:01 AM - SPINE: Poller[0] NOTE: Spine will support multithread device polling.
... checking hosts ...
07/24/2015 05:00:07 AM - SPINE: Poller[0] Time: 6.5513 s, Threads: 20, Hosts: 175
# spine stats and weathermap logs not shown!!!
07/24/2015 05:05:02 AM - POLLER: Poller[0] NOTE: Poller Int: '300', Cron Int: '300', Time Since Last: '301', Max Runtime '298', Poller Runs: '1'
07/24/2015 05:05:02 AM - SPINE: Poller[0] NOTE: Spine will support multithread device polling.
... checking hosts ...
07/24/2015 05:05:08 AM - SPINE: Poller[0] Time: 6.2672 s, Threads: 20, Hosts: 175
07/24/2015 05:05:58 AM - SYSTEM STATS: Time:56.7614 Method:spine Processes:1 Threads:20 Hosts:175 HostsPerProcess:175 DataSources:19646 RRDsProcessed:16695
# spine stats for 5:00 pooler (359sec but timeout set to 115sec)
07/24/2015 05:06:00 AM - SYSTEM STATS: Time:359.0849 Method:spine Processes:1 Threads:20 Hosts:175 HostsPerProcess:175 DataSources:19646 RRDsProcessed:16695
07/24/2015 05:06:32 AM - POLLER: Poller[0] -1437703501.2414 seconds
# then weathermap log duplicates
... logs ...
07/24/2015 05:06:38 AM - WEATHERMAP: Poller[0] [Map 2] monitoring.conf: About to write image file. If this is the last message in your log, increase memory_limit in php.ini [WMPOLL01]
07/24/2015 05:06:38 AM - WEATHERMAP: Poller[0] [Map 2] monitoring.conf: About to write image file. If this is the last message in your log, increase memory_limit in php.ini [WMPOLL01]
07/24/2015 05:06:38 AM - WEATHERMAP: Poller[0] [Map 2] monitoring.conf: Wrote map to /var/www/cacti-0.8.8f/plugins/weathermap/output/29ddbf1d776632cd8840.png and /var/www/cacti-0.8.8f/plugins/weathermap/output/29ddbf1d776632cd8840.thumb.png
07/24/2015 05:06:38 AM - WEATHERMAP: Poller[0] [Map 2] monitoring.conf: Wrote map to /var/www/cacti-0.8.8f/plugins/weathermap/output/29ddbf1d776632cd8840.png and /var/www/cacti-0.8.8f/plugins/weathermap/output/29ddbf1d776632cd8840.thumb.png
07/24/2015 05:06:39 AM - WEATHERMAP: Poller[0] STATS: Weathermap 0.97c run complete - Fri, 24 Jul 15 05:06:39 +0300: 2 maps were run in 7 seconds with 0 warnings.
07/24/2015 05:06:39 AM - WEATHERMAP: Poller[0] STATS: Weathermap 0.97c run complete - Fri, 24 Jul 15 05:06:39 +0300: 2 maps were run in 7 seconds with 0 warnings.

I can't understand what it can be, can someone help? (same problem with spine 0.8.8b and 0.8.8f). I checked my system load at this time everything is OK (la 0,8 - 1,0; 2 CPU Xeon 5160@3,0 (2core)).

My cacti info:

# General Information
Date Fri, 24 Jul 2015 10:15:13 +0300
Cacti Version 0.8.8f
Cacti OS unix
SNMP Version NET-SNMP version: 5.5
RRDTool Version RRDTool 1.3.x
Hosts 182
Graphs 7722
Data Sources Script/Command: 20
SNMP: 558
SNMP Query: 16602
Total: 17180

# Poller Information
Interval 300
Type SPINE 0.8.8f Copyright 2002-2015 by The Cacti Group
Items Action[0]: 19627
Action[1]: 19
Total: 19646
Concurrent Processes 1
Max Threads 20
PHP Servers 8
Script Timeout 115
Max OID 20
Last Run Statistics Time:10.1265 Method:spine Processes:1 Threads:20 Hosts:175 HostsPerProcess:175 DataSources:19646 RRDsProcessed:16485

# PHP Information
PHP Version 5.3.3
PHP OS Linux
PHP uname Linux mondomon 2.6.32-504.23.4.el6.x86_64 #1 SMP Tue Jun 9 20:57:37 UTC 2015 x86_64
PHP SNMP Installed
max_execution_time 120
memory_limit 512M

mysql 5.1.73

p.s. - Sorry for my english.