Settings that solve some weird vim behavior like starting in REPLACE mode (put this at the end of your vimrc)

terminalfix.vim

" Terminal fixes
"
" These originate from some linux distribution's system vimrc. I can't say
" that I understand the details what's going on here, but without these
" settings, I've had problems like vim starting in REPLACE mode for
" TERM=xterm-256color (neovim is fine)

if &term =~? 'xterm'
    let s:myterm = 'xterm'
else
    let s:myterm =  &term
endif
let s:myterm = substitute(s:myterm, 'cons[0-9][0-9].*$',  'linux', '')
let s:myterm = substitute(s:myterm, 'vt1[0-9][0-9].*$',   'vt100', '')
let s:myterm = substitute(s:myterm, 'vt2[0-9][0-9].*$',   'vt220', '')
let s:myterm = substitute(s:myterm, '\\([^-]*\\)[_-].*$', '\\1',   '')

" Here we define the keys of the NumLock in keyboard transmit mode of xterm
" which misses or hasn't activated Alt/NumLock Modifiers.  Often not defined
" within termcap/terminfo and we should map the character printed on the keys.
if s:myterm ==? 'xterm' || s:myterm ==? 'kvt' || s:myterm ==? 'gnome'
    " keys in insert/command mode.
    map! <ESC>Oo  :
    map! <ESC>Oj  *
    map! <ESC>Om  -
    map! <ESC>Ok  +
    map! <ESC>Ol  ,
    map! <ESC>OM  
    map! <ESC>Ow  7
    map! <ESC>Ox  8
    map! <ESC>Oy  9
    map! <ESC>Ot  4
    map! <ESC>Ou  5
    map! <ESC>Ov  6
    map! <ESC>Oq  1
    map! <ESC>Or  2
    map! <ESC>Os  3
    map! <ESC>Op  0
    map! <ESC>On  .
    " keys in normal mode
    map <ESC>Oo  :
    map <ESC>Oj  *
    map <ESC>Om  -
    map <ESC>Ok  +
    map <ESC>Ol  ,
    map <ESC>OM  
    map <ESC>Ow  7
    map <ESC>Ox  8
    map <ESC>Oy  9
    map <ESC>Ot  4
    map <ESC>Ou  5
    map <ESC>Ov  6
    map <ESC>Oq  1
    map <ESC>Or  2
    map <ESC>Os  3
    map <ESC>Op  0
    map <ESC>On  .
endif

" xterm but without activated keyboard transmit mode
" and therefore not defined in termcap/terminfo.
if s:myterm ==? 'xterm' || s:myterm ==? 'kvt' || s:myterm ==? 'gnome'
    " keys in insert/command mode.
    map! <Esc>[H  <Home>
    map! <Esc>[F  <End>
    " Home/End: older xterms do not fit termcap/terminfo.
    map! <Esc>[1~ <Home>
    map! <Esc>[4~ <End>
    " Up/Down/Right/Left
    map! <Esc>[A  <Up>
    map! <Esc>[B  <Down>
    map! <Esc>[C  <Right>
    map! <Esc>[D  <Left>
    " KP_5 (NumLock off)
    map! <Esc>[E  <Insert>
    " PageUp/PageDown
    map <ESC>[5~ <PageUp>
    map <ESC>[6~ <PageDown>
    map <ESC>[5;2~ <PageUp>
    map <ESC>[6;2~ <PageDown>
    map <ESC>[5;5~ <PageUp>
    map <ESC>[6;5~ <PageDown>
    " keys in normal mode
    map <ESC>[H  0
    map <ESC>[F  $
    " Home/End: older xterms do not fit termcap/terminfo.
    map <ESC>[1~ 0
    map <ESC>[4~ $
    " Up/Down/Right/Left
    map <ESC>[A  k
    map <ESC>[B  j
    map <ESC>[C  l
    map <ESC>[D  h
    " KP_5 (NumLock off)
    map <ESC>[E  i
    " PageUp/PageDown
    map <ESC>[5~ 
    map <ESC>[6~ 
    map <ESC>[5;2~ 
    map <ESC>[6;2~ 
    map <ESC>[5;5~ 
    map <ESC>[6;5~ 
endif

" xterm/kvt but with activated keyboard transmit mode.
" Sometimes not or wrong defined within termcap/terminfo.
if s:myterm ==? 'xterm' || s:myterm ==? 'kvt' || s:myterm ==? 'gnome'
    " keys in insert/command mode.
    map! <Esc>OH <Home>
    map! <Esc>OF <End>
    map! <ESC>O2H <Home>
    map! <ESC>O2F <End>
    map! <ESC>O5H <Home>
    map! <ESC>O5F <End>
    " Cursor keys which works mostly
    " map! <Esc>OA <Up>
    " map! <Esc>OB <Down>
    " map! <Esc>OC <Right>
    " map! <Esc>OD <Left>
    map! <Esc>[2;2~ <Insert>
    map! <Esc>[3;2~ <Delete>
    map! <Esc>[2;5~ <Insert>
    map! <Esc>[3;5~ <Delete>
    map! <Esc>O2A <PageUp>
    map! <Esc>O2B <PageDown>
    map! <Esc>O2C <S-Right>
    map! <Esc>O2D <S-Left>
    map! <Esc>O5A <PageUp>
    map! <Esc>O5B <PageDown>
    map! <Esc>O5C <S-Right>
    map! <Esc>O5D <S-Left>
    " KP_5 (NumLock off)
    map! <Esc>OE <Insert>
    " keys in normal mode
    map <ESC>OH  0
    map <ESC>OF  $
    map <ESC>O2H  0
    map <ESC>O2F  $
    map <ESC>O5H  0
    map <ESC>O5F  $
    " Cursor keys which works mostly
    " map <ESC>OA  k
    " map <ESC>OB  j
    " map <ESC>OD  h
    " map <ESC>OC  l
    map <Esc>[2;2~ i
    map <Esc>[3;2~ x
    map <Esc>[2;5~ i
    map <Esc>[3;5~ x
    map <ESC>O2A  ^B
    map <ESC>O2B  ^F
    map <ESC>O2D  b
    map <ESC>O2C  w
    map <ESC>O5A  ^B
    map <ESC>O5B  ^F
    map <ESC>O5D  b
    map <ESC>O5C  w
    " KP_5 (NumLock off)
    map <ESC>OE  i
endif

if s:myterm ==? 'linux'
    " keys in insert/command mode.
    map! <Esc>[G  <Insert>
    " KP_5 (NumLock off)
    " keys in normal mode
    " KP_5 (NumLock off)
    map <ESC>[G  i
endif

" This escape sequence is the well known ANSI sequence for
" Remove Character Under The Cursor (RCUTC[tm])
map! <Esc>[3~ <Delete>
map  <ESC>[3~    x