Test case 'Monitored Item Service ->Monitor Basic->010.js' (and probably others with header timestamp check) finish with:

"CreateMonitoredItems.Response.ResponseHeader.Timestamp shows a delay in excess of 1100ms, which exceeds the configured tolerance
of: 100 msecs."

The server need 20 ms to respond. The overhead of about 1000 ms is because the ResponseHeader.Timestamp is set too early (createMonItemsRequ.RequestHeader = UaRequestHeader.New( { Session: session } );) After setting the timestamp additional script work is done. In this case:

"// turn the MonitoredItems parameter into an array, if not already; then add to the request."

Which takes about 1000 ms. (using 5000 Monitored Items).

Proposed solution would be to set ResponseHeader.Timestamp as late as possible before sending.

Related ticket: 0006402: Time tolerance warnings