I, too, had installer issues with B17. My normal procedure is to download the installer into a unique directory, start it, and killl any V12 or later TCC instances; the installer is instructed to remove only the previous build of the save version (would be overwritten anyway) but retain all older versions (currently going back to 4nt5). On my desktop system it apparently installed all, but instead of reporting that it finished it offered to "add features/repair/remove". On my laptop system I used option/u; it finished successfully. Comparison of files showed that in fact B17 was successfully installed on the desktop, but the installer displayed a false alarm. B17 actually runs succesfully.
I also had all those left-over tcmd.msi files, deleted manually.