Running 1.10.3 on Windows 7 x64. Never had a problem with version updates.
Today I downloaded 1.10.4 and attempted to install it. Got a message to the effect of:
The older c:\Program Files (x86)\MakeMKV is not empty
Well, of course it's not empty. The prior version is installed there.

I haven't bothered manually uninstalling the old version and then retrying, but clearly there's a goof somewhere in the installer routine.
Just FYI. I'll wait until 1.10.5 to update. I don't rent 3D movies which seems to be the headline change in .4.
Marc