I updated 7-zip v. 16.04 to 18.01 but somehow the old version was not properly removed because Pmp though that there is now two versions of 7-zip installed.
Maybe you had x86 of 7-Zip and Patch My PC updated to x64 7-Zip, This is probably why this would happen for 7-Zip,
I had x64, not x86.
I'm talking about the older version that didn't remove, and maybe it was the EXE installer because this x64 is the MSI one, so it may not remove the previous EXE version unfortunately :-\
Noticed the same thing myself - thankfully PMP has a built-in uninstaller... so after a few simple clicks, the old version was removed!
(http://ist3-6.filesor.com/pimpandhost.com/9/1/4/4/91447/4/O/i/s/4Oisb/giphy.gif)
Great! We will also try to improve this more :)