Blender unresponsive / driver issue?

I’ve created a custom rig which uses several drivers. To export my animations (hand animated for use in Unity) I have been going into pose mode, baking the actions to the rig and exporting the NLA strips in an .fbx export.

Until this morning this was all working perfectly…

Now, for some unknown reason, when I go to bake the animation it’s taking a very long time. I’ve left it running for hours (whereas before it took minutes) and all I can see is ‘Blender Unresponsive’ on my Activity Monitor (I’m using Blender 2.79 on a Mac) It seems to be doing something but it seems something is quite wrong.

I’m completely stumped about what is causing this error but have noticed a few observations/ideas below:

  • there is a ‘reloaded trusted’ button at the top of the screen next to which is written ‘driver var’. This has been there for a while and is in relation to one of the armature drivers. In the past I pressed ‘ignore’ and was still able to bake animations. When I press ‘reloaded trusted’ the head on my animation becomes contorted.

-I experimented with deleting all the drivers and encountered the same problem

-I’m in Blender Cycles (but could change to Blender Render if that’s preferable)

-In the bake action option I’m selecting ‘visual key framing’ and ‘clear constraints’

-I tried opening the same file on a different machine with a different instance of Blender and encountered the same problem.

I would really appreciate any help/ideas as I’m working to a deadline and I have no idea what to try next. The hand animations took me a really long time so I really hope there is a solution!