LuaSourceContainer Is the deepest instance you can reach in Roblox’s engine, it is what every single Script-Type uses to function.
This error is one of the few errors that you cannot really fix nor does it cause any issues, the error is caused by the Roblox Studio Software.
Edit: Depending on what went wrong in the LuaSourceContainer it has the ability to kill threads, keep this in mind. If it occurs frequently, then maybe file a bug report.