Now I can’t tell, but are projectiles registering against the world geometry? They should leave behind sparks, smoke, and impact decals and I didn’t see any of that in the clip.
Also, try going to the bottom floor and picking up the other two guns to see if they’re also broken. There’s an SMG on some crates in the middle and a shotgun in a multistorey block off one corner of the hex between the stairwell and the area with the ramp.
If all else fails I may just have to upload some sort of build with extra logging enabled to get a printout of what’s going on because your problem makes no sense.
Edit: I’ve added extra logging to the v2.2 update, but you have to launch the game with an extra -v argument from the command line to turn it on. The logs get written to AppData/Roaming/StomyGame/KuromagiJam/output.log. Send me that file through pastebin or twitter and maybe I can find out what’s really going on here.