The arrows you mention are probably the End-Of-Line (EOL) symbols for CRLF and LF respectively.
Picture: https://www.emeditor.com/text-editor-features/coding/multiple-selection-editing/
You can enable the visibility via “View > Marks > Returns” … and “CR and LF with different Marks”.
There should be only one type of that EOL-markers in one file: DOS/Windows (CRLF) -or- Unix (LF).
To change that EOL setting, utilizing “File > Save as…” and chose the wanted line endings from the drop-down menu in that dialog.
Stefan