I've been working on a mod for myself, using several modders resources, tweaking settings, and so on. I used Wrye Mash to make a .esm copy of the .esp so I can then make "temporary" mods off the main file for testing, etc. It worked just fine for a while. Now whenever I change the .esp and use Wrye Mash to "copy to .esm," I get this message:

Traceback (most recent call last):
File "masher.pyo", line 1503, in OnItemSelected
File "masher.pyo", line 1618, in SetFile
File "masher.pyo", line 1001, in SetFileInfo
File "masher.pyo", line 802, in PopulateItems
File "masher.pyo", line 1045, in PopulateItem
File "mosh.pyo", line 2351, in isWellOrdered
KeyError: 1334052419.5308549

When I load the .esm in the construction set, everything looks fine. However, when I load it in-game, not everything from the .esm loads up.

Does anyone have any knowledge of this?

With Wyre Mesh? Not specifically, I haven't touched it. But if you wanted a to use SmartMerger it can do the job for you. Downside is it has to load and categorize the whole file, rather than just changing a 4byte section in the header. (Plus it will sort the records, but shouldn't have any real effect otherwise; Maybe I can create a --header flag to be used for minor changes in that part.. Hmmm...)

./SmartMerger Input.esp --master output.esm

Alternatively if you are only changing the type and not much else, you can use Enchanted Editor and change the file type (either to 1 or 0, not sure which it was just off hand)