Yepppp, another balance shaft failure. Sounds like you have a good handle on it. I think, but someone else should confirm, that the cam chain tensioner is pressurized by the oil pump. Pretty sure the little spring in there is just to keep it tensioned while the engine is shut off. Low oil pressure could explain why your timing was jumping around. I can't tell by the picture, but it looks like the guide still had some meat on it.