It is effectively similar to a ModAct, yes. I am afraid that the log.lst tells us very little. Here are the offending lines:
[9:49:46] Zero Square processed from com.maddox.rts.SectFile@7ed8b4
[9:49:46] java.lang.RuntimeException: Zero Square processed from com.maddox.rts.SectFile@7ed8b4
Very oddly, the problem appears to be related to the 3d model and/or textures. If I load the heir.him in DrJones I get some error messsages relating to the null.msh. I swapped the 3d files for those from the Alpha2 version (non-409), and this removed the complaints from DrJones. But, the same error persists. The crash (non fatal) is at 45% with the afore mentioned 'zero square' notice.
More curiouisly, if I substitute these He 115 3d model files for the He 111 H2, the game will start the mission and render the He 115 correctly, but upon exiting the mission I get a fatal error (frozen process, must End Task) without any message box.
Baffling. I have never before seen the likes. This behaviour is consistent on the same game install on two different PCs and three different operating systems.