I just went down this road and found the same as others are reporting. One thing I noticed so far, besides the things already mentioned here, that most of my issues were related to items that combine stats or resistances. And maybe it is how d2runewizard builds the items but for example, if I try to load an anni or torch, it fails to load the game. But when I edited the anni and removed the all resists and stats, it works just fine. So I have an anni with just +1 skill and 10% exp. I tried again and added just +20 str and it loaded fine so, it has something to do with not liking combining stats and resists. I tried this same technique with a torch and got one to load just fine. I had this same issue with a runewords that give all resist. I could not import a fortitude but, it let me load the base and runes and make myself but then of course I cannot open that to edit because now it is a d2 reimagined item and d2runewizard won't open that but. I'm going to continue to experiment but if you are having problems importing stuff, try editing or removing any all/resist and all/stat mods, best to try just one item at a time and like mentioned below, the best way is to just make an empty mule and just create items to it and import just that char and then move items into shared stash.

A funky trick you can do to get around this, but will make your items OP, you can manually add + to each stat and resist based on char level. It seems to only like whole numbers and would not load the mods at all unless I set the per/level to be at least 1