I'm not sure if it makes any difference, but did you just switch to Burton boots this year? A couple years ago when buying my first pair of boots I tried on a bunch. I tried 5-6 different models of Burton's and found that the heel/ankle area put some weird pressure on my ankles. Every pair felt like the padding meant to hold my heel in place was to high for my ankles, every time I would step down it felt like my ankle and heel were separating a little putting strain on the ligaments and tendons. Maybe they just needed to be packed out a little so my heel would sit all the way down without putting pressure on my ankle
I just figured if they were uncomfortable walking around the store for a few minutes no sense in taking a chance that they would be that way all the time. I did try on a couple pairs of DC and the ankle part felt fine but the toe box felt very skinny and I hate having my toes smashed. I finally found a pair of Van's that fit my weird shaped foot/ankle.