Okay, so I thought it used to be possible take a carefully updated mod, replace an older version used by an existing character and have it still work right. But now I get the old nasty doubling bug. I'm trying to update my Mannequins For Sale mod (mainly to add wigs), and here's why I'm confused:

1. I AM making sure the date is the same, I'm not that rusty.
2. I'm using the code patch so the above shouldn't matter anyway.
3. I updated this mod before without trouble. I can freely "hot swap" versions 1.1 and 1.2, but not my new 1.3 update.
4. Weirdest of all, this seems to happen if I merely load and save the mod in the editor without changing a thing.

Now I realize there's an easy solution, just add four words to the readme "sorry, not backwards compatible." But I'm much too stubborn to settle for that. What's going on here?

Im having the same trouble trying to update an old mod of my own.

Anybody got any clues?

ObjectIndexes getting reordered maybe?
http://wryemusings.com/Wrye%20Mash.html#Doubling


Basically, give some things like this a try in mash:
http://wryemusings.com/Wrye%20Mash.html#ModUpdating

I thought it might be something like that, but I didn't remember (or maybe never knew) exactly how it worked. So in a nutshell, if I add or remove any references, as opposed to other types of content, then most likely save games will need to be "Mashed" before they can use the update safely. Right?

So here's my next question, are there any utilities to correct for this in the mod, rather than the save game?

Nope. Instead of "sorry, not backwards compatible", I'd use something like "not backwards compatible unless you use Mash updaters feature. You can update a previous save using a Mash updater this way:
From Mash Mods tab:
- right click new version mod, Updaters..., select old version mod
From Mash Saves tab:
- click old savegame, right click old version mod, change to... new version mod, Save