2.5.73-mm2 ftp conntrack/nat not working

Normally, people access the ftp server with passive mode. This worked with my previous kernel on the router, 2.4.18. After updating, the box seems to miss the last packet(s) from the ftp server or client when finishing a transfer, such as a list or changing directory when using passive mode. I'm fairly sure it is a problem in one or both of the netfilter ftp modules because when not DNAT'ing the packets (ie. when accessing the server from the router itself) everything works as expected. I'm not aware of any netfilter patches in the mm2 patchset so i think this is also a problem with the stock 2.5.73 release. Can anyone else verify the problem or have experience with something similar. Active mode seems to bypass the problem, further suggesting the netfilter modules i think?