OK, I found something that might help–the debug file for the update.
2018-12-07T23:05:23.041Z - Creating “Brave (old)” shortcut on desktop
2018-12-07T23:05:24.150Z - Attempting silent install using “C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe”
2018-12-07T23:05:50.773Z - Creating “Brave (old)” shortcut on desktop
2018-12-07T23:05:51.327Z - Attempting silent install using “C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe”
2018-12-07T23:05:54.642Z - Error thrown when installing brave-core: Error: Command failed: C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe /silent /install
2018-12-07T23:06:02.798Z - Creating “Brave (old)” shortcut on desktop
2018-12-07T23:06:04.318Z - Attempting silent install using “C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe”
2018-12-07T23:06:32.875Z - Error thrown when installing brave-core: Error: Command failed: C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe /silent /install
2018-12-07T23:06:52.768Z - Error thrown when installing brave-core: Error: Command failed: C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe /silent /install
2018-12-08T03:34:53.775Z - Creating “Brave (old)” shortcut on desktop
2018-12-08T03:34:56.083Z - Attempting silent install using “C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe”
2018-12-08T03:35:02.103Z - Creating “Brave (old)” shortcut on desktop
2018-12-08T03:35:02.602Z - Attempting silent install using “C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe”
2018-12-08T03:35:24.484Z - Error thrown when installing brave-core: Error: Command failed: C:\Users\User\AppData\Local\Brave\app-0.26.0\resources\BraveBrowserSetup64.exe /silent /install
2018-12-08T03:35:58.797Z - brave-core already installed at “C:\Users\User\AppData\Local\BraveSoftware\Brave-Browser\Application”
2018-12-08T03:35:58.797Z - Launching brave-core at “C:\Users\User\AppData\Local\BraveSoftware\Brave-Browser\Application/brave.exe” with “–upgrade-from-muon” flag