:source should be without quotes:
E471: Argument required
E484: Can't open file /Users/anyaji/.opam/4.09.0/share/ocp-indent/vim/indent/ocaml.vim
This file doesn't exist on my system, but as you can ...
The help for 'titlestring' says:
When Vim was compiled with HAVE_X11 defined, the original title will be
restored if possible, see |X11|.
As you don't have X11 Vim won't help you.
In Bash you could use the environment variable PROMPT_COMMAND. The command defined in this variable is executed before the prompt is displayed (see man bash).
Setting LANG to tr_TR.UTF-8 did solve the issue.
Turns out LANG being empty was the root cause:
I only checked through ...