Update FAQ.md (#3812)

Author: TheGreatRambler

Documentation/LanguageServer/FAQ.md

@@ -1,12 +1,17 @@
 # Frequently asked questions
 
+* [Why are my files corrupted on format?](#why-are-my-files-corrupted-on-format)
 * [How do I get IntelliSense to work correctly?](#how-do-i-get-intellisense-to-work-correctly)
 * [Why do I see red squiggles under Standard Library types?](#why-do-i-see-red-squiggles-under-standard-library-types)
 * [How do I get the new IntelliSense to work with MinGW on Windows?](#how-do-i-get-the-new-intellisense-to-work-with-mingw-on-windows)
 * [How do I get the new IntelliSense to work with the Windows Subsystem for Linux?](#how-do-i-get-the-new-intellisense-to-work-with-the-windows-subsystem-for-linux)
 * [What is the difference between `"includePath"` and `"browse.path"` in **c_cpp_properties.json**?](#what-is-the-difference-between-includepath-and-browsepath-in-c_cpp_propertiesjson)
 * [How do I re-create the IntelliSense database?](#how-do-i-re-create-the-intellisense-database)
 
+## Why are my files corrupted on format?
+
+This is likely due to the fact that you either have a multi-root workspace where one folder is a child of the other, or you are using symlinks to open your file. Reduce the folders in the workspace to one and remove the symlink. This should fix your problem.
+
 ## How do I get IntelliSense to work correctly?
 
 There are two IntelliSense engines present in the extension: the "fuzzy" engine (or Tag Parser), and the new "Default" engine. If you are using version 0.11.0 or higher of the cpptools extension, then you can preview our new IntelliSense engine which has more accurate auto-complete suggestions and tooltips. To use the new engine, you need to ensure that `"C_Cpp.intelliSenseEngine"` is set to `"Default"` in your settings. Since the engine is still in preview it is not on by default for everyone yet.