This old post is the closest I can find to what I'm seeing, error message reporting a different line number than shown in the scripts editor. The scripts editor wraps a line twice at 2048 characters before chopping at total length 4150 near the start of the 3rd line of random letters. It echoes the long line as if it's a single line, except that the script editor's line-counter increments for each of the 3 lines.
To reproduce:
1. Run this command in an editbox then paste the clipboard into any script:
//clipboard alias longlinetest echo -s $regsubex($str(x,2050),/x/g,$base($rand(0,1295),10,36,2))
2. Paste this line as the line immediately following the above paste:
alias testscriptline echo 4 -s $scriptline | echo -s $null
3. The #1 long line displays as if it's pasting a short line, followed by 2 long lines plus a final short line, and when you move the cursor among the 4 lines, the line-counter shows as if they're 4 different lines. However if you run the /longlinetest alias, the echo contains the content of all 3 rows of random letters displayed in the editor, so I know the script lines aren't being chopped within 4150.
When you run the /testscriptline alias, the displayed scriptline and error message both show the true scriptline which is 3 less than the line number shown by the script editor.
The limit for displaying lines is characters not bytes, as it does allow a UTF-8 encoded line to be longer than 12k bytes, using this as a substitute for creating the #1 alias above:
//clipboard alias longlinetest echo -s $str($chr(10004),4100) $+ x
