Apologies if this question has been answered a 100 times in the past, but I have taken a three year break and need to catch up on quite a few things that seem to have been deleted from the forums.

I am going to the give you the background to the question, before leading into it. I have been playing about with using Wrye Bash's bit-flipping function to perform ESP Mastering on Iliana's Elsweyr the Deserts of Anequina mod to add some additional quest content. This seemed to work pretty well. However, then I spotted that Iliana had released an update I had not installed. So I installed it, this overwrote her .esp file with a new version (with the same name).

This utterly stopped my mod of her mod dead (straight crash out of the Construction Set) which after some trial and error I got around by using Wrye Bash's Add Master ability to manually make my mod realise that it needed that it still needed ElsweyrAnequina.esp as a dependency, as it seemed to have lost that information somehow (I would not really have thought that was expected behaviour, but I have never done it before so I assume it is?)

Now, this provided mixed results. Everything I had created or modified was preserved, with the exception of around two-thirds of the actual cell references. That is to say, while any cell references relating to placing content already present in either the Oblivion.esm or ElsweyrAnequina.esp were all preserved, many (but not all) cell-references relating to records I had created were simply deleted from their cells.

So firstly, Is this the expected behaviour from such an operation? Secondly, if so, is their a known work around?

I was thinking I could make a 3rd esp that was dependent upon ElsweyrAnequina.esp, and then make my esp dependent upon both ElsweyrAnequina.esp and the new third .esp so all new content was provided by what the .esp would assume was a Master. But that means chaining esp-masters, which seems somewhat over-complex.

tes4gecko patch function may work has you could compare the New Version to your Version and get the changes that you made split out that may work.

When the subject of an Esp-master is changed, there are three possible things that can happen.
1) Your mod added new content - not affected, it's still new content
2) Your mod overwrote existing content - it now either still overwrites it, or it has become "new content" because the original was deleted. Either way it should work - sort of, because...
3) Your mod made a reference to existing content. - if anything was deleted that was referenced, your mod now breaks. If the items referenced have changed, so that the things you do to them aren't valid any more, your mod breaks. This can happen to vanilla content that is deleted by the mod in between, which is why many folks recommend never deleting vanilla things, just moving them out of reach below ground, so that scripts won't crash etc., but that's not usually considered when going from one release of a mod to the next. Mod authors treat their own content as deletable between releases as they assume they're the only users.

Unfortunately the third category is the big one. It's really hard to create anything that's purely one of the first two cases.

Corepc's recommendation is appropriate here, but expect to do a lot of work over again. Modding a mod is always shooting at a moving target.

Thanks.

I was aware It would probably have issues, I just wanted to make sure I was not missing a trick to get around it.