In the vimrc file the following snippet overrides the location of the viminfo file from the home folder to ~/.vim/dirs folder:
So, deleting the viminfofile in this folder solves this error.
The problem is with the = in your command. It's being taken as part of the expansion for the mapping.
That's triggering the = command, which typically reformats a block of code. Since you have a space after the =, that's being swallowed as the "motion" for = (which is roughly equivalent to the motion of going right one character.)
I guess this reformatting ...
The .vim/plugin directory is not where you want to unpack your plug-ins! (Yes, I known the name would suggest so...)
If you want to use Vim 8 packages (which I believe you do), then you should unpack it under a directory named ~/.vim/pack/*/start, where the component after pack can be named anything (suggestions are bundle, vendor or your username.)