SSMS wont give up file associations

I have installed SQL Server Management Studio v17.9 on a clean Windows 10 installation. This associated all .sql files with SSMS. I want to associate .sql files with a plain text editor (eg: Sublime) but I am unable to change the default application.

If you are running Windows 10 1803 or 1809 this is a known confirmed bug. The bug first appeared on PCs running Windows 10 April 2018 Update Build 17134.320 (KB4458469) which was issued on October 9. It also appears on PCs running Windows 10 October 2018 Update Build 17763.55 (KB4464330) which was also issued on October 9th, 2018.

For those machines running the April 2018 Update, Microsoft issued a patch KB4467682, in order to address this issue on November 27th, 2018. For those machines running the October 2018 Update, Microsoft issued a patch KB4469342, in order to address this issue on December 5th, 2018.

Addresses an issue that prevents some users from setting Win32 program defaults for certain app and file type combinations using the Open with… command or Settings > Apps > Default apps.

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