When I use a fast file appender it seems to start from the beginning of the file every time, overwriting previous entries. What I mean is that if the program starts, then I start again. The previous entries at the very beginning of the file are overwritten.
It's possible that the fact that the entries span multiple lines might make it worse. Either way it always seems to start at the beginning of the file, instead of at the end (like log4j 1.2.x did).
Maybe I need to try the regular file appender instead of the fast one and see if the same behavior occurs.
I'm not at my workstation so I can't recreate it at the moment, but if you have trouble recreating it let me know.