The memory increase is fixed in version 18.104.22.168.
To mitigate the memory increase a factory reset
can be performed after the initial upgrade.
For example if a patch upgrade to 22.214.171.124 has already been performed, choose an .nru image of 126.96.36.199 to upgrade the rescue partition. Once the .nru image has been installed reboot the SSL Visibility appliance from the serial console and choose the "Factory re-install" option. If the rescue partition is already loaded with a 3.9.x image proceed directly to the factory reset.
Remember that a factory reset will wipe out the current configuration, and the appliance will need to be bootstrapped again, so ensure to backup everything on the SSL Visibility appliance before proceeding.