A very strange bug has suddenly infected myself and a friend's playthrough roughly halfway through The Nameless Isle which has since spread to our older save games in the same playthrough, as well as affecting entirely new save games. Bear with me as I explain it as best I can, thanks.
The game had been running flawlessly for us for (according to the save game timestamp) 33 hours and 18 minutes, whereupon we had a gap of about two days. After coming back to the save today my friend's game outright crashed every time he tried to join at a specific point in his load bar. Meanwhile for me hosting absolutely everything functioned normally. Immediately I tried to rule out it being that specific save that was broken by loading an older save in the same playthrough and having him join that, which he could but with things severely broken from his perspective, such as equipped armour pieces suddenly becoming unidentified, having 0 durability, being renamed, sudden weight changes for seemingly random items, the entire skill bar replaced with random skills playable characters shouldn't have etc.
Our next attempt to figure out exactly what was going wrong involved me sending him our save file for him to host and instead I to join. First I sent him our latest save which caused the same problem for me as it did him, I crashed repeatedly at a specific point. Then I sent him the older save, I had the exact issue he had. Lastly in that vein of attempts we tried to start a brand new game with him hosting it. When I loaded in as Lohse I had absolutely no gear apart from the source collar and I had again a skill accessible only to NPCs (Fiery Malediction specifically, with a question mark for an icon) and as the host his game had 0 issues.
Naturally we assumed it had something to do with our mods even though neither of us had gained or lost any since the last time we played when things worked perfectly normally and we had been making a genuine attempt to have our directories match as closely as possible even if he would automatically install whatever I had when he joined me. We both disabled all of our mods and tried the previous joining methods, exact same result in each case. As a last ditch effort we tried to outright delete our mod folders and the game's .dll and then verify the game cache through Steam. No change.
I would like to repeat the most frustratingly odd part of all of this: Since the last time we played with 0 issues nothing has changed. No mods, no configurations, no hardware, no software. We both experience the exact same thing whenever we try to join each others game and the host experiences none of the issues the person trying to join does. Unless this is a connection error, which I don't understand how it could be, I can't think of any solution for us apart from just completely reinstalling and hoping it changes something if not for that playthrough than at least for a new one. I'll include the crash dump file as well as an imgur library visually detailing our problem if it in any way helps figure out what this issue is, whether it be user error or something extraordinarily unusual.
As a side-note the crash dump is listed as 22h44m for some reason, which is at odds with the previously listed save game timestamp.
Imgur Library. MediaFire link for the crash dump. 
