Anyone know if there is a way to manually apply the patch?

I clearly made a mistake by using my backer version of the game on GOG instead of steam.

Yeah, I feel the same way. Should have redeemned my backer key on steam. There is no wasy to apply the patch manually. If you switch off auto updates and try to install it manually, you get the same error message.

And they don´t offer a seperate download.

This issue has been resolved as 0089 is out now.

I can't update, all I get is not authorised. I have verified the game files and reinstalled the client.