What to do about "Optimized and serialized model data is different from source model data, from file (blah, blah)"?

I received the subject message after inserting my models into the SDK and
attempting to build the package. The above message is followed by:
modelDataOne.images == modelDataOther.images". I am wondering what does this
mean and what can I do about it? I tried deleting the file (a .gltf) and it
resulted in many more error messages, so I started over. Following these
errors, everything looks good except “Skip mirroring due to command failures.”
I assume this is a result of the errors described above. The build stops while
reloading texture files of the models. Any help will be greatly appreciated.

So the problem was that all .gltf, .bin, .xml and .png files were not of the
same date and time. Over some time period I had apparently copied some of the
files from one source and others from another source ( I had copied the files
to two or three computers). When I copied the source files to the computer
with the issue, things worked. Note that this also caused another problem: Two
of the models placed for the same airport showed pink textures instead of the
texture they should have displayed. This issue also went away when the source
files were used, even though the model with the “Optimized and serialized
model data” issue was not one of them!