Hi Daniel,
Strange issue indeed. I was unable to find any reference to log.text in our sources. Basically, the output will happen if LlSetDebug is called with the LlDebug.LogToFile flag. You should check your source code for this call. The file name is probably set via LlSetOptionString with the LlOptionString.LogFilePath enum value.
You should avoid calling LlSetDebug altogether, as @Hans_Peter_Reische pointed out this will slow down processing considerably. If you can’t find the options in your code, also check the config file of your app. The options might have been set there using these settings.