A few days ago, I installed wxWidgets 3.2.3. In order to make my life easy for me I have an environment variable WXVERSION (now 3.2.3) and another one WXWIN with %WXPATH\WXVERSION (%WXPATH being the location on the drive with lacking version info.
When compiling an existing project, it was still using the older 3.2.2.1 libs. I checked the complete project, workspace and global configuration for remainders of 3.2.2.1 but couldn't find any.
After I added the WXWIN variable directly to the project, it worked all of a sudden.
Conclusion: in some cases the environment variables are not re-read and processed by the builtin makemake utility.