AE CC 2014 Error upon closing project "...layer named '10' is missing or does not exist...

Question

Upon closing (or quitting) an After Effects CC 2014 project I'd been working on for several days I'm presented with the following error message dialog boxes 39 times:
In this comp I've masked the same piece of video into 38 triangles to create a transition effect.  I named those layers "1" to "39" for organization.  There are another 39 layers (the flip side of those triangles that come into view when I rotate the main triangles), and the masks of those layers are pick-whipped to the corresponding primary 39 layers.
Despite this error message, nothing is visibly wrong in the project.  The video that's the source of those layers is NOT missing.  I can see it.  It's a 1920x1080 Apple Pro Res 422 Quicktime, sitting in the same folder as a bunch of other clips.  If it WAS missing wouldn't I see the color bars placeholder?  t tried reimporting the clip and option-dragging it back into those layers, but I get the same message.
Upon opening the project I get this message, 39 times:
Again, the software is apparently confused, thinking that something is missing when it's not.
So is this very complex project corrupted now?  That would be a drag.  At least it still seems to work, I just have to hit "OK" on these dialogs 78 times to open and close the project.  I was expecting more for $50/month.
Thanks.
Shawn Marshall
Marshall Arts Motion Graphics

Answer 1

We found what the culprits were, but I don't know why they'd cause these error messages.
To recap, I have a piece of HD video that I've duplicated 39 times with a different triangular mask on each layer to re-create the whole frame (moving the anchor points of each layer as needed).  The idea is that I then rotate those layers in 3D somewhat randomly, revealing a different video clip on the back side.  To create the "B-side" video for the back sides I duplicated the original 39 faceted layers and parented each to its corresponding "A-side" piece.   I created some opacity expressions to make the A-sides disappear halfway through their rotation with the B-sides appearing at the same point.
My plan was to vary the mask shapes on the A-sides to create variations on the transitions, so I enabled an expression on the masks and pick-whipped the mask shapes on the B-sides to their A-side counterparts.  That seems to be the problem.  Here's the expression (applied to layer 26B):
thisComp.layer("26").mask("Mask 1").maskPath
I repeated this for all 39 B-side layers.  Then I duplicated that comp and inserted new video into the transition.  At some point some part of the software decided some layers were missing or something, creating the above error messages.  The comps still worked as designed; it was just error messages that I had to repeatedly dismiss.  Once I deleted all of these mask expressions the error messages stopped.
Before deleting those expressions we tried renaming the layers (1-39) so they were unique within each comp (Train1, Rail1, etc) but that didn't work.
Feels like a bug.
Shawn Marshall
Marshall Arts Motion Graphics