One Host effects Another Host when Added

[low10sws6]

I Have a 3750 Switch Stack of 7 switches at 97.3

everything time i add this switch stack as a host monitoring stops for a few hosts that are also switch stack in a different part of the building and items for these host start to get backed up in the queue and they stop being monitored

their are also another 98 hosts being monitored that are unaffected

i have know problems pulling snmp data via proxy server snmpwalk

These are monitored VIA Proxy

Any ideas???

is this a zabbix problem or a network problem

[low10sws6]

If I Clear the history for the host on the item and remove the template queue is cleared from the items that were stuck and got backed up when adding the host