As stated above, whenever I touch either my pedals or my wheel in any way I get a ‘Controller Disconnected’ message. I hit enter to reset and the game continues only to have the same error appear the next time I touch something. In other words, this game is totally unplayable right now.
So much for ‘early access’.
I had similar issues using the DD1 PS4 base and SimTrecs Pro GT Pedals. If you put the wheelbase in 2.5 compatibility mode it seems to work better.
Having the same issue with my DD1 and Heusinkvelds. 
Can confirm that compatibility mode fixed it and I can now use and map my wheel and pedals.
I had the same issue mentioned above, now in 2.5 mode, its working, but looks like the throttle input doesnt give 100%. Any tips how to make it work properly? I use my setup for Assettos & rFactor & this was supposed to be fun, it´s a bit of struggle instead right now.
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Seems like it is a known issue for some wheels. https://support.forzamotorsport.net/hc/en-us/articles/4409616884883-FH5-Known-Issues