Agent endless loop on update_cpustats()

[stratos]

I have a heavy loaded server (120 LXCs) where zabbix agent used to work without issues.

With no apparent reason, other than more load on the server the agent returns only empty values.

log has this:

3061:20130712:221940.019 In send_buffer() host:'zabbix2.stratus5.com' port:10051 values:0/10000
  3061:20130712:221940.019 End of send_buffer():SUCCEED
  3061:20130712:221940.019 Sleeping for 1 second(s)
  3054:20130712:221940.866 In update_cpustats()
  3054:20130712:221940.870 End of update_cpustats()
  3061:20130712:221941.021 In send_buffer() host:'zabbix2.stratus5.com' port:10051 values:0/10000
  3061:20130712:221941.021 End of send_buffer():SUCCEED
  3061:20130712:221941.021 Sleeping for 1 second(s)
  3054:20130712:221941.871 In update_cpustats()
  3054:20130712:221941.872 End of update_cpustats()
  3061:20130712:221942.021 In send_buffer() host:'zabbix2.stratus5.com' port:10051 values:0/10000
  3061:20130712:221942.021 End of send_buffer():SUCCEED
  3061:20130712:221942.021 Sleeping for 1 second(s)
  3054:20130712:221942.880 In update_cpustats()
  3054:20130712:221942.881 End of update_cpustats()
  3061:20130712:221943.021 In send_buffer() host:'zabbix2.stratus5.com' port:10051 values:0/10000
  3061:20130712:221943.021 End of send_buffer():SUCCEED
  3061:20130712:221943.021 Sleeping for 1 second(s)
  3054:20130712:221943.881 In update_cpustats()
  3054:20130712:221943.882 End of update_cpustats()
  3061:20130712:221944.039 In send_buffer() host:'zabbix2.stratus5.com' port:10051 values:0/10000

I have tried increasing buffer size, timeout, agents with no luck. The same behavior is appearing on 1.8.11 and on 2.0.6 (i have upgraded the agent and connect to a new clean server).

Communications is ok between server and agent. No firewalls blocking. Just the agent in an endless loop... (should i file a bug?)

Any hints?

Thank you in advance.