Duck egg incubation question

[HorseDad]

We noticed tonight during candling that one egg seems to be stuck to the membrane or have some sort of issue with the veins. It almost seems like there may be blood inside the egg.
If anyone has any info on what this could be, I'd love to hear it. Should we remove the egg? Hope it hatches? The wavy lines are throwing me off. Roommate is concerned it's a bacterial infection, but I really don't think it is. It looks like this embryo is stuck on one side. It is still moving, miraculously, but it does not look good.
Images of the egg from all angles:

 

[KathiQuacks]

What day is this egg on?
How often is it being turned?
I don’t think it’d hurt to leave it. I’d check on it again in a few days. You’re right that it looks weird. It doesn’t look like an infection, though.

 

[HorseDad]

What day is this egg on?
How often is it being turned?
I don’t think it’d hurt to leave it. I’d check on it again in a few days. You’re right that it looks weird. It doesn’t look like an infection, though.

We've been turning them twice a day religiously, as well as misting them. This worked perfectly for our last batch and I'm just very confused about this one egg. June 6th is our first hatch day (since ducks sometimes take a bit longer and all) so we are on day 18-19 (it's midnight here). We are ~10 days out from hatch. All the other eggs seem a lot more developed with normal veins and good air sacks, which has me questioning what happened with this egg. This is the same egg that looked a little "off" in the beginning — we thought it was dead, but it's still surviving despite everything. Not convinced it will hatch, but not counting it out yet, either. These pictures don't show the air sack very well on this egg, but it's oddly small.
I've never seen this strange wiggly line in an egg before, even in a stuck embryo. Usually they're relatively straight, if a bit curved. Very strange. I've seen some similar things in eggs that have died, where a blood ring, when I haven't caught it early, began to squiggle, but he is very much alive.