BUCK file under a toplevel "device" directory doesn't invalidate caches properly

Here's a weird one. I've been working on moving an existing project over from Makefiles to buck2, and I noticed that the contents in the toplevel directory 'device' (//device/BUCK file) doesn't pick up edits properly. I need to kill buck2d and restart for it to see them.

I didn't actually try to debug this one, I figured I'd file the issue first. I can look into doing a repro case if needed, just let me know. Thanks!