We were experiencing some trouble applying hotfix 4.1.9 to our installation, which had previously been patched up to 4.1.4. I believe I've tracked the issue down to a DLL which exists in 1-4 but not in 5 or higher: cms.kenticofactory2.dll

Removing that file from the bin directory of our installation seems to have made the problem we were seeing go away. I'll have to do some more testing to confirm, but I do note that cms.kenticofactory2.dll appears in the hotfix packages for 4.1.1 through 4.1.4, and doesn't appear in 4.1.5 or higher. I don't see it in the 4.1 installer package, either.

Is this a known issue? I couldn't find any reference to it in the instructions for 4.1.9 or 4.1.5.