I have saved the setup as a template, where the 828 is the Master device and Clock Mode. This seems to work ok but sometimes resets itself to just use one driver (after starting up). Any idea why?

This is not a Montage question and is best posed to Mark of the Unicorn.

I am also running Montage Connect which so far is running fine too (but really miss using patch lists).

Patch lists limit you to selecting Presets and become less useful when using sounds you've customized (User, Library, etc) Montage Connect deals with YOUR Montage sounds be they Preset, User, or Library, it simply updates your capture whatever you are using in your Montage. Patch lists limit your thinking because it is only as current as the day it was made. A Patch list made for the Montage made at the start of this year if frieghtfully out-of-date now as new Presets were added in a firmware update, besides it not being aware of what's in your User Bank, or what you have installed in your Libraries.

There are currently 2036 Preset Performances
There are 5760 potential other Performances your "patch list" will not (cannot) know about. And most importantly the list will not contain YOUR custom creations. If you miss the way you selected sounds, learn to do so in the synthesizer (not the computer). The way MONTAGE CONNECT works is when ONLINE and "AUTO SYNC" is active, it automatically runs in the background, and it will capture all YOUR current settings for the Performance you use.