Gooday,
I find that my Regex is a bit rusty. Because when I tried with Regex101.com I got an other result than in Alteryx.
I'm trying to parse the underscore away and I only needs the last 2 characters.
so in this example I only need AA_FH to be FH and the AA_OUT_FH to also be FH.

In Alteryx I get this back

Did something change in the Regex tool?