Hi GigasightMedia,
I made a few attempts today to build the Engine from source code from the 4.13.0-Release tag (currently the same as the Release branch), and did not see any of the errors that you mentioned. At step 7 of your repro steps, I tried building both the UE4 project, as well as the entire solution, and both times the build completed successfully. I tried doing some rebuilds as well and didn’t have any errors with those either. Do you happen to have any additional information about this issue that may be helpful?