I can confirm this; using the reset lever makes the Hugger-girl boss unkillable (she takes damage but can't be defeated).
Edit: The above only holds for the 0.10 build. I just now saw the .12 update and will test it out there.
Edit #2: The .12 update appears to fix this on multiple bosses. Special attack openings may not show up, but bosses are killable, even on reset.