For reference. Our 2015 Fusion Hybrid had the brake booster replaced a couple of months ago at just under 16K miles for this very problem. Yeah, we don't drive much. The dealer indicated there was a service bulletin on the issue but it was not a warranty repair. Fortunately we had purchased the Ford extended warranty so the repair was completed for the $100 deductible. I didn't realize hybrid brake jobs were such a big deal if fluids need to be drained. They told me the bleed process alone with the regen brakes is a 4 hour job so this would have been a very big bill if not for the warranty. It's been working fine for the last 500 miles. This had been happening intermittently almost since we bought it, freshly ordered and delivered from the factory in late 2014. Early on, the dealer never found a code even if the check brake system light appeared when it happened. It started to occur more frequently and I finally got it to code while in the dealer lot after a couple of attempts. I noticed as it was getting worse that after putting it in gear and releasing the brake, it would just sit there without moving forward. Eventually after a lag of a few seconds it would engage and move forward. I never could 100% reproduce the issue, but it happened more often after setting the parking brake or pressing on the brake in Park to the point where the hydraulics may have been engaged over the electronic braking system. In any case, it appears to be fixed now. I looked at this post several months ago and it spurred me to follow up on the issue, so I thought my experience might be helpful to others.
