The game calls INT 21/55 to create a child PSP, but DOSBox does not copy the parent's command line into the child. Seems pretty straightforward to fix:

1bool DOS_ChildPSP(Bit16u segment, Bit16u size) {
2   DOS_PSP psp(segment);
3   psp.MakeNew(size);
4   DOS_PSP psp_parent(psp.GetParent());
5   psp.CopyFileTable(&psp_parent,true);
6+  psp.SetCommandTail(RealMake(psp.GetParent(),0x80));
7   psp.SetEnvironment(psp_parent.GetEnvironment());
8   psp.SetSize(size);
9   return true;
10}

It also looks like real DOS copies both FCB entries as well, but the game in question doesn't care about it.

A note to the DOSBox devs: the game is triggering the stack wrap E_Exit at execution in SVN builds.

does changing the e_exit to a log message make it work ?
(e.g does it work with the current implementation ?)

Yes, the game runs with the E_Exit removed. It's a case of SP=0 in the executable header, which isn't problematic like SP=2 used to be, but just reporting because that's why the E_Exit is there. 😉

well they will become log(log_exec,log_error) before the release 😀

How safe is that cmdtail fix ? it looks pretty safe to me, but their are more ways to create psps.

I mostly copied that line from DOS_NewPSP(), so it seems reasonably safe, assuming that the method of determining the parent is the same in all conditions. However, you might want to observe what DOS does with the FCBs to decide if that should be handled as well.