right....hi-tops. these are notorious for farting because when they are laced all the way up, the back of the heel moves when you step and rubs on the material at the back. examine your shoes very carefully to see if the sole is intact, or if there are holes/dips/movement between the different layers. if they are structurally ok, you can try the following:
*not lacing the shoes all the way up to the top, but as you would for a normal trainer
*they are leather - i would not wash them, but stick them in a warm place to dry out (airing cupboard or above radiator)
*keeping your feet as dry and non-sweaty as possible - cotton socks and powder
*only wearing one pair of socks - two will cause more friction
try some or all of these to see if you can isolate the problem. for me it is not lacing them up all the way. it could be something as simple as that! good luck x