We just rolled out TE 12.6 and our run last night did fine with /SilentMode set. The problem MIGHT be with the ForceConversion switch. That switch only triggers when you use the SilentMode switch. So, something is being converted in your project or there is some sort of error in the conversion. Have you checked the silent log as indicated in https://support.smartbear.com/testcomplete/docs/working-with/automating/command-line-and-exit-codes/command-line.html?
Actually there shouldn't be anything to convert. I use 12.6 TC also. /forceconversion is just in case if there is something to convert in future.
I run TE as normal user, from command line.
silent.log is not modifed after upgrade and neither new is created when i rename it as .old
Access rights should be okey, I checked them.
Just out of curiousity, what happens if you run it with /SilentMode but without /ForceConversion?
