A friend and I were up on the Strathfarrar hills last weekend and got to the first top in quite thick cloud, so thought we'd better take a bearing. My friend got out his quite new (two years old at most) Silva Type 4 compass and, after a quick glance at it, pointed the way ahead. However, the ground became much steeper than it should have been, and quite craggy, so he took another bearing, but quickly expressed concern that the needle wasn't settling properly.
I then did a check on my much older Silva Ranger, according to which we were about 140 degrees off course. Comparing between the two, it was obvious there was something wrong with the Type 4, which was behaving very strangely. It wasn't 180 degrees out, which I know can happen, nor had the damping fluid got out.
My friend assured me he hadn't had it near any electronic equipment or strong magnetic source, so I can't explain what caused it to go wrong. It did make me wonder if there's been a batch of duff Type 4s.
I'd agree with those asking for something without a waterproof membrane; they're a waste of time in a shoe. Leather uppers would be my preference, for durability and a measure of water resistance. And a good deep lug pattern, also as mentioned.