Strange behavior of vim

 I have been using vim for many years, but it has lately been behaving very strangely. I have autoindent and autowrap set, but vim appears to ignore them while editing some files.

Note: *some* files. The exact same vim process will work properly on some files and misbehave on others.

My .vimrc:
---------------------------------------------------------
set autoindent
set nohls
syntax off
set tw=72
set ws
set ic
set ts=8
set sw=4
map <F2> :n
map ^N :n
:np <F3> :w
:e #<F4> :w
map <F5> :e #
map v k$hjl
map = 3k$h3jl
map @ k$hjl
map q F r
map v f r
set background=light
set ff=unix
let loaded_matchparen=1
set fo+=tcroqj
filetype off
---------------------------------------------------------

Note: I copied "set fo+=tcroqj" from somewhere; I no longer remember what it does.

Relevant facts:
1. version: VIM - Vi IMproved 8.2 (2019 Dec 12, compiled Feb 13 2022 22:15:51)
Included patches: 1-4372

2. In the recent past I upgraded my copy of cygwin (unix emulator on Windows) to  the latest version.  

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