Receive Notifications for not changed MonitoredItems|OPC UA Standard|Forum|OPC Foundation

Hi, i'm working on schneider PacDrive 3 PLC with OPC UA.
The client is on PC.
The server is on PLC.
I've a big number of variable in the PLC code.
The client create one session and one subscription, with one MonitoredItem for each variable on PLC.

If the variables on PLC code are declared "BOOL", everything works. The right notification is received by the client.
But if the variables are declared "BIT", for a single change the client receive 8 notifications, one of these for the real changed MonitoredItem, and others 7, for the MonitoredItems that are write near at the first item in the PLC code!

Example:

PLC---------------PLC after change--------------Notification on CLIENT

var...---------------- var....
var....----------------var....
var1 false-----------var1 false------------------------ var1 true
var2 false---------- var2 false-------------------------var2 true
var3 false ----------var3 true-------------------------var3 true
var4 false ----------var4 false ------------------------var4 true
var5 false-----------var5 false-------------------------var5 true
var6 false---------- var6 false-------------------------var6 true
var7 false-----------var7 false-------------------------var7 true
var8 false---------- var8 false-------------------------var8 true
var...----------------var...
var....----------------var....

It seems a samplig problem.
There are any options that i can activate on client or on server, to fix this problem?

Thanks.

NEWS:
The client receive notifies even if the change happens on non monitored Variables.
More precisely:

...
var1 monitoredItem
var2 monitoredItem
var3 NOmonitoredItem
var4 monitored
...

the change on var3, that haven't a subscibed monitoredItem, provides notifications for var1 var2 var4 on Client!

It seems that OPC UA Server sampling a byte on "channel/bus/addressSpace" instead a single bit.