Hi, @Sergey Sharybin (sergey). The forum discussion is just to contextualize my problem, but reading it is not necessary to replicate the problem in this report.

I can confirm that something has changed from 2.78 to 2.79. I have a custom keymap and have this exact same problem.

Thanks, @ronan ducluzeau (zeauro), I appreciate the feedback.

Thanks for the quick reply, @ronan ducluzeau (zeauro).

Running into this issue again. Could this be possibly be fixed with the new depsgraph or something?

Oh, forgot to respond to this. The exporting itself works just fine for me.

There should be as I've also confirmed this with a co-worker.

Ah, sorry, it was late, haha. Here's the file:

For when you get around to it:

In case it helps, just wanted to add on that thing that seems apparent to me in my tests is that exporting .fbx out of Blender bakes the animation as if basically all the options for Bake Action are checked.
Whereas, when importing the .blend into Unity straight, the baked animation is as if only the "Only Selected" option is checked (which, in this case, seems to be the desired setting).

Thanks for the suggestions, @Bastien Montagne (mont29). I tried changing the Simplify value to different values (including 0), as well as the Sampling Rate just in case, but nothing seems to help. =/

Right, but this doesn't look like one of them. Problem also replicated by co-worker. I'd appreciate it if somebody could look into this.

Ah, actually, it looks like baking within Blender works if only "Only Selected" option is on. (While testing, I somehow came to the conclusion that all the options needed to be checked.)

Yes, but neither exporting to .fbx to Unity nor baking the animation in Blender works corectly. Did it work for you in 2.78c?

Right, though I think it should be noted that, while this may not be a bug, this behavior is fixed by enabling the new depsgraph. Maybe that could be useful. Thanks, Sergey!

@ronan ducluzeau (zeauro) Thanks, that worked like a charm! I'm actually a little disappointed that I didn't think of that myself.

I'm still bumping up against this problem. Are there plans to remedy this limitation in 2.8? Even if it breaks older rigs, I'd be glad to have this limitation removed going forward.

I tried reimporting the .fbx to Blender, and as you said, it works fine. Then I tried importing it into Sketchfab and also Unreal Engine and the animations all work fine in those as well.

Oh, and just in case it's needed, before I change the items in the hierarchy, this is the structure as it imports into Unity by default from the .fbx exported out of Blender:

I tried it but it's still shifting. =/

Oopse, forgot to attach the file:

Hi, Ivan. I appreciate you taking the time to recreating the metarig.
Yes, I did originally make some modifications to the ORG-bones on my rig. I guess I wrongly assumed the z-axis should be facing up..

Oh, wow, nice, it worked! The snipet resolves the issue for me.

Thanks for looking into this. I could think of one thing that possibly could've affected the animation data.

Ah, okay, in retrospect, I realize I should've included the .blend file.

Ah, I apologize, really sorry for wasting your time!

I'm not sure if this would be covered in the scope of this task, but would it be possible to register drag direction as positive?

Well, that's embarrassing.. I thought I checked for that when doing the tests. Sorry for wasting your time, but thanks for checking it out!

Oopse, you're right. My apologies for lying. Just tested on 2.76 and 2.73.
I guess when I was testing this out last night, I accidentally did it for the armature instead of the bone in the other versions, haha.

I'll do you one better than a .blend. Show and tell:

I guess this would be a pretty impossible problem to resolve if it's isolated only to me. As really annoying as it is, I suppose to I'll have to live with it for now.
Perhaps when I upgrade my OS to Windows 10 later on, the issue will be resolved..

Confirming OS updates does not fix the issue.

Since I don't know what causes this, I could only test when it happens, as I was able to do tonight.

Ah, I forgot to mention. This hang time goes away if I remove the "addon" folder where the preferences are stored in the User\AppData\Roaming\Blender Foundation\ folder.

I agree this is a serious issue. Even if technically not a bug, it seems to be a crucial problem to be resolved ASAP.

Haha, okay. If it's not a simple fix, then I guess energy could be spent better elsewhere.
For the time being, setting my own container/codec seems fine so will do that for now. Keep up the good work!

Ah, I see. Thanks for the reply. I did a test with VLC and you're right about it playing both files fine.

Furthermore, selecting "Lossless Output" renders a visually corrupted file for me:

Ah, I see. That resolves the problem!
Sorry for the bother.. I searched everywhere for an answer but couldn't find the solution anywhere.

Yes, Cycles, probably should've specified that, haha.

Ah, my apologies. The workaround worked like a charm! Makes me wonder why something like this isn't enabled by default, haha.

Thanks for taking the time to explain, krash. I can't say I understand your instructions.. perhaps it's a bit too technical for me, but I appreciate it.

I'd like to add that trackball rotate and edge slide both also seem to be hard-coded.
If they could be changed, it'd also provide a workaround until the "event system" issue is resolved (T40537)

The problem does seem to have been fixed for the 3ds keymap, but, sadly, the problem still remains with my custom keymap.

I wanted to further add that the rapid switching for the "G" key seems to be with the "edge slide" function. Again, this did not happen with 2.68a.

Whoa, noticed a bug. I'm guessing it's related to this one so I didn't create a new bug item.

Awesome, it behaves exactly as expected now!
I guess the only thing left is the difficult Dimensions issue.

Awesome, thank you, that solved it!

Great, glad to see #3 fixed!
Though I'm not sure #2 isn't a bug. Maybe I should've clarified, but I meant to say the value registers even after the mouse is let go of.
Animated gif to showcase the problem: