NTDOC -
Don't think its @CRLF. Comparing FOR/NEXT and my original DO/UNTIL test, failure is occuring in different place with strings of different sizes (+50,000 vs 32,000). Lonkero probably nailed it related to string manipulation. Now where that's failing, unsure since both scripts are building a single string variable of 'x' characters.

Since my final 'solution' writes/appends single characters to the line, not working with any large strings.

Bill