Problems not populating with expected data in ITEM.LASTVALUE2 in trigger names

[RichL]

Hi all,
so I have been doing a lot of reading and was pretty sure this feature was working 4.X before I upgraded to 5.X
(Names of vars changed from real world)

I have a trigger expression as follows
{server1:my_custom_check.last(#1)} <> {server1:my_custom_check.last.last(#2)}

For this example my_custom_check returns a numeric ranging from 0 to 10,000

In the Trigger name I have the following
Server count change from {ITEM.LASTVALUE2} to {ITEM.LASTVALUE1}

What I expect to get when the trigger creates a problem is something similar to
Server count change from 100 to 166

What I get is
Server count change from 166 to 166
so the current value triggering the expression.
This is according to the docs the correct result I believe?

What I want to know is HOW do I get the value before the triggering value, so I get this expected result
Server count change from 100 to 166
(assuming server1:my_custom_check.last(#1)} = 166 and server1:my_custom_check.last(#2) = 100

Trigger name combinations tried so far
Server count change from {ITEM.LASTVALUE2} to {ITEM.VALUE1}
AND
Server count change from {ITEM.VALUE2} to {ITEM.VALUE1}


help/guidance would be appreciated