User config file not properly written with v0.34 (crashes all other Add-Ins)

Using a settings file in Visual Studio (Express 2015) for an ExcelDna based Add-In leads to the following error for me:

- I am using settings with the scope "User" to save some GUI settings
- After using the Settings.Default.Save() method the settings are written to the current user.config file. All settings are properly written to the "userSettings" node, but the "configSections" sections node is missing
- If the "configSections" node is not present in the file yet, it is still missing after the save
- If the node was already there it remains unchanged, so no new section for my Add-In is added.
- The app.config and the .dll.config file look fine and have the correct configSections and the sectionGroup "userSettings"
- After downgrading to version 0.33.9 everything works as expected
- The Add-In itself works fine (even using the config file as expected) but all other Add-Ins that try to access the settings file crash, because of the wrong format