Fixes for all non-cosmetic bugs have been posted in the 12.3.1 thread and will be included in Fetish Core 12.3.1 (which will be uploaded shortly).
I checked the Fetish Locator and it seems to be working fine to the extent the game code allows it to. I was able to move windows, resize them, etc. The fields of "parent.etc." are when the game cannot find the window (in some cases, this happens whenever the window is not visible, nothing I can do about it). In the particular case of the Inventory window that was mentioned, that window doesn't exist anymore so it obviously won't be found. I'll have to remove some of the old chaff like that in a future update, but since it's cosmetic only you can just ignore that for now. The stuff you see if you hit "Refresh" when it's first opened is because you haven't yet selected a window, so it obviously can't find location and size for no window.