Thanks, got it.
Pre-Source Hammer apparently does something... strange, which I hadn't seen before, and which fucks up the processing because Past Me was an idiot while working on the Classic Quake parser (which is what Valve 220 is, mostly)
I've got a fix in the works that'll go live... eventually (I want to combine it with some other changes I'm doing, since I don't have the bandwidth to do multiple rapid updates, sorry)
In the mean time, to unblock you, you can work around the problem by opening your .map file in Notepad++ and running Macro/Trim Trailing Space And Save (or doing it manually through Edit/Blank Operations/Trim Trailing Space) before opening it with HammUEr.