Clip waveform disappearing - why is it happening?

This afternoon I opened a project in 2016.06 which I created with an earlier version of Platinum (but a very recent one - 05 or 04). It contained two guitar tracks, only a couple of minutes long.
 
I then recorded strummed accompanying chords on two more tracks and then saved the project (Menu "File/Save") and shut my PC down.
 
Now, after dinner, I opened the project again and the waveforms on the two new strummed clips are just flat lines, but I can hear what I played!
 
I found the following thread and I did what Zargg71 suggested which is "right click on the clip, choose associated audio files, and click recompute"
 
http://forum.cakewalk.com...s-SOLVED-m3450099.aspx
 
Zargg71's tip worked, but clearly I am not the first person to have this happen.
 
Is this a new bug? Is anyone else experiencing this?
 
The project was newly created in 2016.05 (or 04) and only has these four audio tracks, two old and now two new ones.
No effects, nothing done yet at all. The old tracks are muted, that's all I have done so far.
 
I have repeated the steps but I cannot recreate the bug. It is opening with waveforms displaying correctly now.

Ah, the mysteries of Windows.

This happened to me a couple times - I save projects very frequently, usually after every tracking instance.  I found that if I saved the project before the waveform completed it's rendering (after hitting 'stop' on recording), I had issues with the waveform not being displayed properly afterward.  Not sure if this could be your issue, but ensure you're waiting for the waveform to fully redraw after stopping recording before clicking save to see if that helps.

No, that is destructive. Zargg71's method works just fine.
But thanks for the idea.