Yep, I have both the floppy & CD versions of Tie-fighter + DoE; the CD version works ok, but the floppy is buggy in DOSbox.
I verified the files against another game owner in the UK, he ran the floppy version on an actial old Pentium II PC, with real DOS, and he did not have the problem I saw about a year ago, when I was testing this game again.
There are two issues:
1. Non-crashing issue: there is an error in the tech-chamber where you look at the ships, if you use the left arrow, and scroll backwards in the list, the game keeps showing the tie fighter image for all objects.
(Scrolling forward, one can go through the list and it shows the correct images.)
2. Crashing issue: You can select the missile boat (anytime) in the training chamber, and play some of the tube-navigation ok.
(I think the training selection sets the default ship to use in the combat mission)
If you then go to the combat chamber, once the missile boat has been used, the game crashes in the opening scene.
The error indicates too little EMS memory, but that is not the case.
After this error, you need to select another ship in the training, to be able to enter the combat chamber without crashing.
(Any savegame made after using the Missile boat is corrupt and cannot be used further, so autosave should be turned off when testing this.)
Of note is that with the actual DOS and the old Pentium II, you cannot select the Missile boat at will, you need to go through the training for each ship in order.
This also does not happen in the CD version, only with the floppy version in DOSbox.
I haven't had time to fix my old Pentium to try the game in that environment again. (broken hard disk needs replacing)