Have you added anything to your bars recently?
Several years ago, I bought a cheap out-front mount for a Go-Pro camera. For whatever reason, it created interference between my SRM and PC8, and the power numbers were all wonky. Strangely enough, if I used a Garmin, the power numbers were fine.
Also, I'll second the comments from Chappy about Quarq. I went through three Quarqs in 18 months before giving up and buying an SRM. I kept sending it in, they fixed it, then it would break again. On the other hand, my wife has had two Quarqs that have had zero issues. The only difference is mine was a 130 bcd and hers was 110. Not sure how that factors in, but I've heard similar complaints from folks with 130s.