Not equal xPath query limitations - xpath

Question

I need to find logs from EventViewer in Forwarded Events based on computer name, excluding the ones which aren't interesting for me.
My query is like that
*[(System[(Computer!='comp1')]) and
(System[(Computer!='comp2')]) and
(System[(Computer!='comp3')]) and
(System[(Computer!='comp4')]) and
(System[(Computer!='comp5')]) and
(System[(Computer!='comp6')]) and
(System[(Computer!='comp7')]) and
(System[(Computer!='comp8')]) and
(System[(Computer!='comp9')]) and
(System[(Computer!='comp10')]) and
(System[(Computer!='comp11')]) and
(System[(Computer!='comp12')]) and
(System[(Computer!='comp13')]) and
(System[(Computer!='comp14')]) and
(System[(Computer!='comp15')])]
This query works fine unless I add one more condition
and [(Computer!='comp16')])
After that filter stops working and all logs are displayed.
Notice that if I put comp16 instead of comp15 or instead of comp12 everything works fine. So problem is not in the new condition.
The situation is opposite if I use equality filter
(System[(Computer='comp1')]) or
(System[(Computer='comp2')]) or
...
(System[(Computer='comp15')]) or
(System[(Computer='comp16')]) and so on
Filter works fine with much larger queries.
So why not equal operator does not work in large queries?
EDIT
Filter by EventRecordID has the same problem
EDIT 2
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
<EventID>4624</EventID>
<Version>1</Version>
<Level>0</Level>
<Task>12544</Task>
<Opcode>0</Opcode>
<TimeCreated SystemTime="2017-08-18T17:06:15.595105400Z" />
<EventRecordID>1</EventRecordID>
<Correlation />
<Execution ProcessID="584" ThreadID="7100" />
<Channel>Security</Channel>
<Computer>comp1</Computer>
<Security />
</System>
<EventData>
<Data Name="TargetUserName">userName</Data>
<Data Name="TargetDomainName">DOMAIN</Data>
...
<Data Name="ProcessName">-</Data>
<Data Name="IpAddress">-</Data>
<Data Name="IpPort">-</Data>
</EventData>
</Event>

Answer 1

You haven't shown your XML, but it's hard to envisage an XML structure on which this query makes any sense.
Consider the simpler
*[(System[(Computer!='comp1')]) and
(System[(Computer!='comp2')])]
If there is only one System with only one Computer, then this returns true if the Computer is neither 'comp1' nor 'comp2'. But if there is more than one System, or more than one Computer, and if the Computers are not all the same value, then there will inevitably be at least one Computer that is not 'comp1', and at least one that is not 'comp2', and the predicate will therefore always be true.
Usually when people write A!=B in XPath, they should have written not(A=B).