Multi Firmware Upgrade

We have a Wyse Dx0D model currently at firmware version 8.0_505. We believe it is causing problems with daylight savings time and outlook on the terminal server. Even though the device and the terminal server are correct, Outlook is 1 hour off. This only happens on the Wyse devices. 

We would like to upgrade to the latest firmware version but Dell no longer carries the older versions since you have to do it step by step and there is no cumulative firmware package. Does anyone know where to find older firmware versions for this model and how to choose the correct firmware since there are multiple options to choose from for each version?