Hi,
You may wish to check the wheel brakes themselves, not the pipe connection.
I had an issue where the brakes pressed themselves away from the wheel and began to leak. these are the brake 'disk' type, not the expanding pipe sort.
I checked my pipe fittings over and over before I found the problem, fixed by reassembling the wheel/brake hubs and flat spotting the axle for the grub screw.

Hope this helps,