Tower!3DPro: Errors loading custom schedules, etc.

[MTShipp]

I joined so I could access the custom schedules etc. posted on here. I find that most work but quite a few will hang up the game about 63% or 99% in.

How do I troubleshoot finding the error in the .txt file added?

Here is an example for KRDU files I downloaded.

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Search external data: Extensions/Airfields/KRDU/krdu_gaandlocaltraffic.txt
Timetable: 175
Search airplane type in airplanes.txt: RJ1
 
(Filename: C:/buildslave/unity/build/artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)

NullReferenceException: Object reference not set to an instance of an object
  at Game.CreateAirplane (.Action_t action) [0x00000] in <filename unknown>:0 
  at Game+<LoadMap>c__Iterator4.MoveNext () [0x00000] in <filename unknown>:0 
  at UnityEngine.SetupCoroutine.InvokeMoveNext (IEnumerator enumerator, IntPtr returnValueAddress) [0x00000] in <filename unknown>:0 
 
(Filename:  Line: -1)

GfxDevice: creating device client; threaded=1
GfxDevice: creating device client; threaded=1

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[EliGrim]

I guess the file krdu_gaandlocaltraffic.txt is empty.
Open it with a text editor and if so, insert two slashes // at the beginning of the first line and save the file.
Then try if the schedule will be loaded by the game.