binary packages ignored due to changed dependencies

[hick518]

I have a funtoo server that does all the package builds, and my other servers and desktops specify 'getbinpkg' in order to use the packages created by the primary server.  This mostly works, but I often get messages like "The following binary packages have been ignored due to changed dependencies".  Here is an example.

On my laptop, when emerging @world, I get the following message and nothing gets emerged (all other packages have been brought up to date):

!!! The following binary packages have been ignored due to changed dependencies:

     dev-lang/vala-0.28.1::gentoo

NOTE: The --binpkg-changed-deps=n option will prevent emerge
      from ignoring these binary packages if possible.
      Using --binpkg-changed-deps=y will silence this warning.

Neither of the suggested --bin-pkg-changed-deps options change the message in any way.  Even stranger, this version of vala is not installed on the laptop (nor on the primary server). 

# ego query versions vala
 dev-lang/vala| slot|                 repo
--------------+-----+---------------------
        0.26.2| 0.26| gnome-kit/3.20-prime
--------------+-----+---------------------
        0.28.1| 0.28| gnome-kit/3.20-prime
--------------+-----+---------------------
      * 0.30.1| 0.30| gnome-kit/3.20-prime
--------------+-----+---------------------
        0.32.1| 0.32| gnome-kit/3.20-prime

In other cases, I get this message when I do have the specified version installed.  For instance, on my desktop when emerging @world, I get the following message and nothing gets emerged.

!!! The following binary packages have been ignored due to changed dependencies:

     media-sound/guayadeque-0.4.5_p20170110::gentoo
     dev-util/itstool-2.0.2::gentoo

But these package versions are installed on both the desktop and the server:

# ego query versions guayadeque
 media-sound/guayadeque| slot|                repo
-----------------------+-----+--------------------
      * 0.4.5_p20170110|    0| media-kit/1.1-prime

# ego query versions itstool
 dev-util/itstool| slot|               repo
-----------------+-----+-------------------
          * 2.0.2|    0| core-kit/1.0-prime

In yet another case, I get this message and emerge wants to do an ebuild even though the binpkg is available.  For instance, on desktop #2 when emerging @world:

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  NS    ] sys-kernel/debian-sources-4.14.12 [4.14.2] USE="binary"

!!! The following binary packages have been ignored due to changed dependencies:

     sys-kernel/debian-sources-4.14.12::core-kit

NOTE: The --binpkg-changed-deps=n option will prevent emerge
      from ignoring these binary packages if possible.
      Using --binpkg-changed-deps=y will silence this warning.

However, I can run 'emerge -av debian-sources' on that same system and it will install the binary package:

These are the packages that would be merged, in order:

Calculating dependencies... done!
[binary  NS    ] sys-kernel/debian-sources-4.14.12:4.14.12::core-kit [4.14.2:4.14.2::core-kit] USE="binary" 190,850 KiB

Total: 1 package (1 in new slot, 1 binary), Size of downloads: 190,850 KiB

Would you like to merge these packages? [Yes/No]

All of these machines have the same USE options (make.conf, package.use, epro).  I'm constantly fighting this battle to get the machines to use all the binaries built by the server.  Can anybody shed some light on this?  Am I doing something wrong?  Is it a bug?