ASP.Net Website project fails to build after updating a referenced DLL

So I have an ASP.NET VB website that references several other projects (their DLLS are just put in the site’s bin folder). I need to update a small piece of code in one of the projects, which I have done and it builds fine. However, when I copy over the new DLL to the website’s bin folder it fails to build, and all the Imports statements say “BC40056: Namespace or type specified in the Imports xxx doesn’t contain any public member or cannot be found”, which results in a ton of errors like “is not defined” . There is no reference to the updated DLL in the website project’s properties, but if I put the old version back it’s all fine.

How to use command line msbuild to deploy VS2012 Web Site project without precompiling it?

I’ve inherited a very large VS2012 web site project (not web application) and am trying to automate it’s deployment. There are tons of circular references in the project so to get it to precompile using aspnet_compiler.exe I have to turn on fixednames. The problem with that is it causes the build to take about 20 minutes on my quad core, 16gb ram, ssd developer machine. The previous developer didn’t have to deal with this as he would just copy the whole source to the production web server.