Thanks for your attention to this.
Thought that might be the case at first then realized that when I start with an empty uploaded projects folder on the Mac, the new build.DB file created still contains the erroneous files list.
Cutting to the chase : My conclusion is the problem is on the Windows PC end. (A Dell with up-to-date windows 10 Pro)
The key seems to be the Builder Server User ID in B4I.
If I compile with errors.
Change the User ID in B4I to a clean one - no compile errors
Change the User ID back to the original User ID - the same errors recur
(emptied the Mac Uploaded projects folder between compiles just to be sure)
(switching between projects without emptying the mac, the files copied over switched correctly the mac side looks as it should)
All of the correct files for the project being compiled appear on the Mac, but the list of files in the project in the new Build.db file are from that last successful build for the matching Build Server User ID on the PC.
So in summary, when I first use a User ID it works.
After that it will continue to work for just that project.
BUT If I even change that project's structure, such as adding a new code module, it will no longer work for that project either.
If I remove that code module from the project it complies again.
I don't know where you are storing the info related to the User ID and how it relate to compiles so can't dig deeper with that.
If you tell me where to look I will have a closer look.
I can work around it by managing the build server User ID used for each project.
The problem started when I updated to B4I 6.