Elastic X-form disappearing audio

[blastula]

Switching a track from polyphonic to x-form renders empty audio clips...Silence! I'm on HDX, PT12.5.1, OS 10.11.5 but this has happened in previous versions. Doesnt happen all the time, but sometimes.
Any clues as to what's going on and how to avoid this ?

[blastula]

here's another fun fact.
on the track that i'm trying to elasticize w/ x-form:
i tried this:
undo x-form, audio shows up again (now back to polyphonic algorhythm). O deleted all the clips except one, just to see if the switch to x-form command would behave any better. upon selecting x-form, the audio in the clip completely changed to a different part of the song (instead of the end of the song, the clip now contained the beginning of the song.)
note also, I had trashed preferences just prior to these operations.

[midnightrambler]

Yeah Elastic's always been a bit squiffy. If you chop at some random point within the offending "silent" clip, Tools usually re-calculates and creates a new rendered file. The joy then is that you usually end up with a "lump" sound at the chopped bit....