My Rocna anchor is fantastic, but it always seems to come up into the stem head roller the wrong way round. This looks like the effect of the water flow over it causing it to turn over. Does anybody else recognize this problem?

The good news. :)
I have just fitted what is called an "ultra swivel" which I can confirm turns the anchor over and appears to be a much stronger all round design and construction than the conventional swivels. So this should cope better with the sideways strains. Most swivels are tested in a straight line pull, which is useful, but does not reflect the sideways pull / strain put onto them at times.

The bad news, is that the "ultra swivel" costs a staggering £260. Golden Arrow Marine are the sole UK importers and are based in Shamrock Quay, Southampton.