[Edi]

Don't know if there is. The turn file from the previous turn would also be great, because then it could be observed happening. The thing is, despite my name showing in black and having those fancy wings next to it, I don't actually work at Illwinter, so it's up to Johan now to see if anything turns up. Thanks for this.

That bug has been around for a long time, but it's infrequent enough that it's very hard to get material where it could be pinned down. Best case would be if you run into it again, when item slots are lost, save a turn file then. Especially if two-handed weapons are involved, because that leads to strange situations.