It's kind of embarrassing to admit this after playing (or trying to play) for a couple years; however, yesterday as I was practicing scales I was frustrated that I couldn't get a clean tone when I was playing notes higher up on the D and A strings. So when I stopped to study the situation I noticed that when I'm fretting either of the two center strings in a high position the bow simply can't contact the string because it sits well below the adjacent strings. I'm not at home so I'm using a Yamaha EV104 when I practice to keep the noise down, but I assume that the same would be true if I was home and using my acoustic violin. I assume the curve of the bridge on my Yamaha is pretty standard and the problem would be even worse for those using a flatter bridge.
two center strings in a high position the bow simply can't contact the string because it sits well below the adjacent strings.
Not sure how/where you are checking. Right at the bridge the string can't go below the adjacent strings. The string pushed down to the fingerboard will go below the adjacent strings at some point along length, gets somewhat closer to bridge as you go up in position. The bridge/string height can affects this as well. That said, most normal set-ups give plenty of bowing space; but if trying to bow over end of fingerboard, might be a problem in higher positions.