I tried to upgrade an existing City Sample from 5.1 to 5.41 in place, and that failed. I deleted it and created a new one just fine. It took several hours with all the deleting and downloading, but it worked. I do have the latest Houdini from Nov 2023 with Unreal plugin loaded.
Once you get in City Sample, there are many glitches, particularly with clipping on the elevated freeways. Vehicles will drop through and experience damage as they fall through. It’s pretty fun in a way, very much like a glitch in the Matrix. The sheer size of this thing is awesome, and I’m not complaining. It’s beautiful and I love it.