Started playing under 1.22 (on PC), and I still got the "no Delamain" glitch in The Heist (which looks to be a thing since launch). I've completed every single side mission possible before doing this actual storyline mission. I'm not even a programmer, but seeing as this issue has been persisting for many versions now, I feel like I should help out with the limited knowledge that I have from my experience writing application specifications for developers I've worked with.
On Area Load: Verify that x,y,z position of Delamain model and interaction hitbox is within acceptable x,z tolerances and not below ground level y.
If Verification Passes: Do nothing, no glitch.
If Verification Fails: Despawn Delamain model and interaction hitbox, then respawn both.
On Delamain Spawn Event: Verify that x,y,z position of Delamain and interaction hitbox is within acceptable x,z tolerances and not below ground level y.
Most of the time, it will spawn out of line-of-sight, so all of these tiny actions would go completely unnoticed. This is literally the most BASIC of variable checking executions. These are executions that can already be observed while playing the game, such as NPCs correcting their positions, and even basic AI movement. So I know this is not only possible, but an intern fresh out of school could probably write that script even before their morning coffee. I would really like to actually play the game and experience the story, and I'm willing to wait, but for how long I cannot say.