Writer does not empty the file before writing.
This means: you write 40 lines, okay. You write into the same file - this time, only 20 lines - and the old content stays there, just the first 20 lines get overwritten. Definitely not the expected behaviour (and has caused quite a lot of headache before we detected this).
See attached sample patch.
Writer_Bug.v4p (10.1 kB)