Steps to reproduce:
1. Create host Trapper with:
1.1 trapper item trap
1.2 trigger last(/Trapper/trap, {$H:a,b}) - last(/Trapper/trap) = 0
1.3 user macro {$H:a,b} = #2
2. Start server
3. Send two values to trap item

Result:
Trigger has failed with an error: Cannot evaluate function last(/Trapper/trap,{$H:a,b}): invalid second parameter.

Expected:
Trigger worked without an error.

Note that expression last(/Trapper/trap, {$H:a,b}) works in calculated items and also works in trigger expression if the macro is quoted last(/Trapper/trap, "{$H:a,b}")