Yes the problem is not in the air.ini I replicate your issue with a clean version of HSFX 7.03 that works in both expert mode and normal mode. When I enabled the unlocked FMB I had a 70% crash (the more complicated one) and this is the error in my log file
[13:47:28] Main begin: PlMapActors: No 'Title' in file 'com/maddox/il2/objects/static.ini', section 'buildings.House$House_I'
[13:47:28] java.lang.RuntimeException: PlMapActors: No 'Title' in file 'com/maddox/il2/objects/static.ini', section 'buildings.House$House_I'
[13:47:28] at com.maddox.il2.builder.PlMapActors.configure(PlMapActors.java:1553)
[13:47:28] at com.maddox.il2.builder.Plugin.loadAll(Plugin.java:152)
[13:47:28] at com.maddox.il2.builder.Builder.<init>(Builder.java:3158)
[13:47:28] at com.maddox.il2.gui.GUIBuilder.<init>(GUIBuilder.java:90)
[13:47:28] at com.maddox.il2.gui.GUI.create(GUI.java:166)
[13:47:28] at com.maddox.il2.game.Main3D.beginApp(Main3D.java:849)
[13:47:28] at com.maddox.il2.game.Main3D.beginApp(Main3D.java:508)
[13:47:28] at com.maddox.il2.game.MainWin3D.beginApp(MainWin3D.java:212)
[13:47:28] at com.maddox.il2.game.Main.exec(Main.java:422)
[13:47:28] at com.maddox.il2.game.GameWin3D.main(GameWin3D.java:235)
I have never seen this type of error maybe one of the expert in maps and objects can tell us something
Just to be sure I used the same FMB unlocker with a 4.12.2 modact 5.3 and everything worked as expected