I know this thread is old and marked solved, but it was never actually fixed — the advice here (wait for the train, hug the wall, wait for the boxes) was a survival trick that improved your odds without removing the cause. Posting this because people still land here from Google when the bug ends their playthrough.
The actual cause has now been found by reverse-engineering the game: the moving train in that room is flagged lethal on contact in the game's data files. The train's collision sweep periodically "captures" the player as touching it — even when it isn't visibly near you — and one frame of contact triggers the instant no-ring death. That's why it felt random, and why the timing tricks in this thread genuinely helped: they kept you out of the sweep window. The old theory that "the train's hitbox is stupidly off" was pointing at the right object all along.
The fix is a one-byte change to one file, small enough to do by hand:
In your Omikron folder, back up MESHES\DECORS\STtra03.3DO
Open it in any hex editor (HxD is free) and go to offset 7C478
Confirm the byte there is 08, and that offset 7C484 nearby reads TTain04 (the train mesh name) — that confirms you're in the right spot
Change 08 to 00 and save
It removes only the train's ability to kill on contact — the train still moves and animates normally, and everything else (acid deaths, enemies, the mission, Magic Ring accounting) is untouched. Works on Steam and GOG. To undo, restore your backup.
If you'd rather not hex edit: there's a double-clickable patcher (patch_train.bat — nothing to install) that verifies your file and makes the backup for you, plus the full technical write-up. I can't post links from this account, so search GitHub for "omikron tetra factory fix" — repo is by Osprey-22, MIT licensed, and the whole script is short enough to read before you run it.
Tested end to end: full crossing through multiple train cycles, bomb placement, and a control acid death (still kills, still consumes a ring, as designed). Twenty-six years late, but it's dead for real now.