Hello,
This is unfortunately due to bugs in the PowerShellGet & PowerShell Gallery API that aren't feasible to workaround. Basically, the API is reporting different versions than the package file, which makes working with local/cached packages and remote packages painful like this. However, it seems like it's going to be addressed by Microsoft, finally, in PowerShellget v3.
In any case, given your architecture (i.e. "Machines on our network cannot connect to PSGallery direct due to the firewall and are only allowed to retrieve via this one feed."), we recommend using a Package Approval Workflow instead.
create an 'unapproved-powershell' and approved-powershell feed
create a connector on 'unapproved-powershell' to PSGallery.org
Promote packages from unapproved-powershell to approved-powershell
This will totally eliminate the "bad API" problem as well.
Cheers,
Alana