Illustrator :: AI CS6 (16.0.4) Symbols Lose Transformations Upon Reopening File - But Only Visually

I've created a series of images utilizing symbols.
 
Basically the images are of a box. Each side of the box has different content.
 
I create the side content flat with an encompassing rectangle. Drag all this to the Symbol Panel to create a symbol (no 9-slice no align to grid set). I then take a symbol instance and use Object > Envelope Distort > Apply with Mesh - 1 row, 1 column and proceed to transform the symbol into position on the packaging.
 
This works.
 
I can easily double-click the symbol and edit the side of the package with no problem. Exit symbol editing mode and the symbol instance(s) update. Perfect.
 
Until.....
 
I close the file. Return to it 12-18 hours later and open it to see that visually my symbols are no longer positioned correctly. I click, the symbol/emvelope is still in the correct position, but the preview on screen shows no transformation. This incorrect visual appearnce translates to print and save for web as well. So it's more than simply an inaccurate preview. The symbol has actually broken out of its container incorrectly.
 
To explain further.
 
When I save the file it looks like this:
 
The grey box indicates the symbol/envelope bounding area.
 
When I reopen the file the next day it looks like this:

The symbol/envelope is still in the correct position but the symbol contents are completely incorrect. There seems no way to reset the symbol other than to delete what's there and redo the transformations.
 
There is nothing overly complicated about the artwork within the symbol. It's all text or line art, no effects or transformations within the symbol itself.