Long story short:
What could I be doing to my Armatures, meshes, etc, or maybe inside the FBX export settings, that could suddenly make the exporter exponentially slower / potentially indefinite? The same file exported in ~10min last week. A few small changes (the file should actually be smaller now) and the export never ends.
I'm relatively new to blender, having only used it for ~2yrs, but I can't for the life of me get a clear understanding of what makes an export take ~10min or under (to make a <20mb FBX file, nothing crazy), and what makes the same file take potentially forever (I stopped it after 20+ min after being convinced something was horribly wrong).
The latest issue came after duplicating an armature, deleting the copy's actions and changing the bones a little (a skeleton variant of the originial armature).
Based on my own experience, the exported FBX of this new armature and the few objects attached to it (no animations added yet) should come out to under 5mb at the very most, and should take less than 5min, but goes indefinitely. The original armature and its many objects (basically the whole file minus the new stuff, so just the old file) now also doesn't export. I'm using the "Selected Objects" checkbox in the exporter to do this.
These FBXs will be imported into Unity afterwards, if that helps.
Some tips I already know / already tried:
-making the file smaller in general / reducing vertex count etc -making the animations smaller - animations make up the bulk of each file
FBX export settings: =under "Main": -check the "Selected Objects": this helped a while ago when this same issue was happening. I think back then it was just a file size issue and this just reduced the time each export took, since I was only exporting smaller chunks as opposed to the whole thing. Now this doesn't even help. Selecting only a small group of objects makes it never end. -deselect "Empty", "Camera", and "Lamp". makes sense, not sure if it helps. -some people say to use the "!EXPERIMENTAL! Apply Transform" checkbox but I couldn't get a straight answer anywhere on what that does exactly. =under "Geometries": -uncheck "Apply Modifiers" after manually applying them beforehand. This didn't seem to change anything. =under "Armatures": -check "Only Deform Bones", this doesn't help either. -uncheck "Add Leaf Bones", I actually use these leaves in my Unity project so I need them in. =under "Animation": -uncheck "All Actions", this makes it finish super fast after not includng any of the animations that should be there.
All other settings I've mostly just left the default values.
Using the blend file within Unity directly has also been suggested. This means Unity automatically uses Blender in the background to export the .blend into an FBX and use this ne hidden FBX instead. That means Unity is now sitting indefinitely because that's what Blender is doing. So no luck there either.
Could my new Armature still be retaining the animations from the original Armature somehow and just making the file much larger? It wouldn't explain how the original Armature also refuses to export after exporting a nearly identical version last week.
Once again mainly I want some general tips on what could potentially be causing Blender's FBX export to stop - not just for this situation in particular because I'm sure it could be any number of reasons and I'll run into a new FBX export roadblock next week. This is the 4th time my entire project has to stop dead because of Blender's FBX exporter.
Any expertise would be very much appreciated!