> About 98% of the time the errors -start- in the -5th- decade like these:
>
> 123456789 123456789 123456789 123456789 56789 123456789
>
> 123456789 123456789 123456789 123456789 1789 123456789
>
> 123456789 123456789 123456789 123456789 89 123456789
>
> *Almost* *never* does the error start in the 4th decade.

This is all consistant with buffer overrun as has already been pointed out
to you.  The buffer is probably near empty before the clear screen.  That
takes longer than it takes the buffer to fill, losing some characters
after the buffer fills.  You would expect the symptom to be partway into
the line just like you show.

Again, fix the overrun problem.  Many ways to achieve this have already
been suggested.


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