The latest REDDOXX Appliance firmware is Build 2032 SP2 (Version 2.2.1242)
The Release Notes, as well as known issues, can be found in the Appliance Administration Manual.
Information regarding the latest hotfixes to the firmware is also listed there:
The latest REDDOXX SimplexGate Gateway firmware from 16.03.2018 is Build 18.0.0 (Version 2222)