fisheye commandline backup result in OOME and broken zip-file

We use command-line backup to automate backup process
java memory options: -Xmx1536M -Xms1536M -XX:MaxPermSize=196M -server -Xshare:auto -XX:-UseGCOverheadLimit -XX:MaxNewSize=128m
command line for backup: /fisheyectl.sh backup --compression 9 -f ${BackUP_DIR}/${FSY_FILE}
As result of this command, we get broken zip (about 13 MiB) and OOME: see attached log fragment

After this we get random exceptions in log, until we restart fisheye

We tried rise -Xmx to 2G, but result is same, and this is a limit on 32bit java, (64 bit java is not recommended for fisheye).

We tried backup via web-interface, same result: broken zip and OOME in logs

How can we do backups?