Importing an Android lightmap for a scene takes 15 minutes in Unity 5... why?

We have roughly sixty scenes that we're importing from Unity 4 into Unity 5 that each have 3~4 lightmaps. While this amount of data certainly took a while to import before, now we're seeing import times that vary from 1 minute to 15 minutes *per texture*.

This import has been running for about 16 hours now and is at only 10% complete.

Please advise!

 

The lightmaps are 2048x2048 and compressed (not sure specifically which compression on Android). I'm not entirely sure what our plans are around lightmapping moving forward. It just seems incredible that a 5 MB 2048x2048 texture would take 20 minutes to import!

The import has now been running for ~40 hours and is about 50% complete. At this point, there's no point interrupting it -- we're populating the cache, so hopefully nobody else will have to go through this lengthy process.

Thanks!