This effect, looks like the staircase effect on some older printers, it was remedied by interchanging the carriage returns and linefeeds on the printer driver.
I am not saying that this will solve the problem, but it could be that the end of line control code is not correct for the QDOS screen driver. It should be something like - CHR$(10);CHR$(13)
If there were _any_ control characters at the occurences of the linefeeds, that would provide a hook for fault search. But they seem to occur by chance :-(
> <The Q > L was o > ne o > f Sir Cl > i > ve Sinclair's ho > me computers.>
All the best Peter