Leaks from around the spindle of Danfoss shoe valves seems quite common. Both of the 2 port valves on my CH system have suffered this problem. The usual advice is to replace the whole valve, but the problem (in my case ) seemed confined to the 'O' ring seals - the spindles and bores were not excessively worn and cleaned up nicely. Danfoss don't supply 'O' rings and won't tell you what size they use in their valves. So I measured the bore and the spindle diameters with vernier callipers and used information from the internet on 'O' ring sizing to determine the correct size: 1.78mm cross section x 6.35mm internal diameter. I used Viton 'O' rings, obtained from Simplybearings.co.uk, lubricated with silicone grease. These worked a treat: no more leaks (so far!). The dimensions are the same for both 22mm and 28mm valves.