My partner has long had a tendency to suffer from medial malleolus pain from ski boots, which can get bad enough to stop her from skiing. Some years ago, while skiing in Fernie, she had work done on her boots and liners by the bootfitters there which helped a great deal (punching out of the shells and cutting out material from the liner, IIRC), but after a few weeks of skiing the pain came back.
So two years ago she went to see a highly respected (and excellent) bootfitter (a regular on here), who set her up with some new boots (Salomon Idol 85CS) on which he did some extensive fitting work to reduce the pressure, although there was limited scope for punching out the shell at the main pressure point because of the location of a rivet. But whatever he did worked - problem solved, pain free skiing! Or so it was, at least, for the next six weeks of skiing - but now the pain is back again. The initial trigger seemed to be an afternoon of ski touring, where she had the boots slightly looser, and I wonder whether that might have meant a kind of backwards and forwards motion over the area which caused a problem. But since then, the boots have come to be more painful on her medial malleolus for normal downhill skiing as well.
The obvious question is why it seems to be OK for a few weeks after work being done, and then the problem recurs? My own conjecture about this is that it might be that the liners are packing out somewhat and thereby meaning her ankles are not being held in quite the same position. I have ZipFit liners and I wonder whether these might work for her, too, on the basis that they don't pack out at all over time. But I'd be very interested to hear of any ideas the experts have about this. It's really affecting her skiing enjoyment.