Why is SPList.GetItems(SPQuery) returning always the same item to different SPQueries?

Hi,

I have this powershell code:

$url = 'http://artemis/customers' #web URL
$ctx = Get-SPServiceContext 'http://artemis' #site URL
$scope = New-Object Microsoft.SharePoint.SPServiceContextScope $ctx

$web = Get-SPWeb $url
$listSyncZakazky   = $web.Lists["bcs_Datis_t_synchronizace_Artemis_zakazky2"];  #BCS to MSSQL 2005 database table
$listMain = $web.Lists["Zakázky"]; #custom SP list

$camlQuery = New-Object Microsoft.Sharepoint.SPQuery
[Microsoft.Sharepoint.SPListItemCollection]$itemsLSyncZakazky = $listSyncZakazky.GetItems()
#foreach ($itemLSyncZakazky in $itemsLSyncZakazky) {
foreach ($itemLSyncZakazky in $listSyncZakazky.Items) {
## happens for both of the ^above^ lines
	$camlQuery.Query = "<Where><Eq><FieldRef Name=`"CisloZ`" /><Value Type=`"Text`">" + ($itemLSyncZakazky["cislo_zakazky"]).TrimStart("0") + "</Value></Eq></Where>"
	$camlQuery.Query
	$camlItems = $listMain.GetItems($camlQuery)
	foreach ($item in $camlItems) {
		$item["CisloZ"]
	}
	$camlItems[0]["CisloZ"]
}

$web.Dispose()

<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">404</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">300</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">306</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">400</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">200</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">206</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">40303</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">40300</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">40301</Value></Eq></Where></Query>
404
404
<Where><Eq><FieldRef Name="CisloZ" /><Value Type="Text">5801</Value></Eq></Where></Query>
404
404

No matter what I do, from the second item in the collection I get the result from the first one although the CAML query is clearly modified. I tried to create new external content type, have the CisloZ column type as number and text and no matter what I do I always get the same result.

I use similar code elsewhere and it is working. What could be wrong here?

Martin