I don't know about the freezing, but the flashing is caused by the very first line in your ~/.vimrc, namely :set vb, which enables visual bell, i.e. flashing instead of beeping.
Vim keeps freezing/hanging when scrolling out of bounds
I don't know about the freezing, but the flashing is caused by the very first line in your ~/.vimrc, namely :set vb, which enables visual bell, i.e. flashing instead of beeping.