I just made a fresh blueprint project, and setup the nodes as they are in the second picture in my original post (with the select node connected to ++). I used a fresh actor blueprint, but any blueprint should work. Then I compiled, and got the warning (macro.log).
Then I restarted the project and set it up like in the first picture, with the select node connected directly to Set (by ref). This crashed when compiled, and is recorded in direct.log
If there is anything else I can do to help, let me know. There aren’t any additional steps that I can think of, beyond making sure the Set (by ref) / ++ nodes are connected by execution pins (as they are in the pictures).