I've tried to run the Pentagon mission twice now for the weekly project, firstly on Heroic with a matchmade group of randoms (someone else was lead), then again solo on Hard (to speedrun and get it over with). Both times as soon as I/we got the marauder's health down by maybe 20-50%, the game threw a delta-03. Reconnecting put the whole group back at the start of the mission.
Looking on the discord, I see others complaining about the same thing in different circumstances - eg being unable to complete Liberty Island.

I have yet to test this more fully (eg, is it every marauder in every circumstance? I completed legendary Roosevelt last Tuesday without a hitch) but figured I'd post this now as it seems like a pretty major problem if it's blocking players from completing WONY, and I'll add as I do more research.

Frustratingly, research will be slow as I have to run the whole mission again to reach the drone (and having completed the weekly invasion, I won't have any 'aerial recon' marauders in DC to test on).

I know the title sounds implausible, but I had one Delta 03 crash while fighting one of the large drones in the open world. Didn't think much of it, had zero issues until I got to the rooftop fight with a marauder drone on the Pentagon mission. As I was fighting it, it was delta 03 disconnects constantly. After defeating it (thankfully my progress on the fight was remembered after each disconnect) connectivity cleared up entirely. It's either one heck of a coincidence or there's something odd triggering with the drone.

EDIT: The rooftop fight was a few hours later, so that should rule out a short stint of spotty ISP service.

@astahl45 It's not only you, I already made a thread about this only about an hour ago. I went back in to record the errors occurring, and this time it saved my progress so I was able to complete the mission, though I got 4 disconnects in the process. I'll post the video in the thread I created once it's done processing.

Update: Upon re-running the mission in order to record the issue, I found that this time the game saved my progress after each disconnect, so I was able to complete the mission. I've attached the video for reference, the four disconnects occur at approximate timestamps of:
00:39, 02:46, 03:11 and 05:11.

The timing of the disconnects seemed to be pretty random, not linked to any specific event.

@the_kettle Great, thx for helping confirm.

I've encountered this bug on 5 occasions now where engaging the Marauder drones causes the game to Delta-03 error. I see I'm not the only one experiencing this but I want to aid in bringing attention to it as it's getting pretty game breaking for me personally as my Marauder Drone patrol is not despawing. I would like to add however that doing weak point damage to the drone seems to instantly cause the error to trigger, although the error will still trigger even if you do not shoot back. Hopefully a fix will come swiftly.

Further update:
I ran this again as a shepherd when another player running it called for backup (Hard difficulty).
The delta-03 happened as usual and we both got put back to the start location of the mission when we reconnected. However, the mission areas stayed clear of enemies, we were able to run through the whole set of areas to reach the final point. At the final area, there was no sign of the marauder or any other enemies, and we were unable to interact with the computer to start the download, so the mission was effectively uncompleteable.

@astahl45 Same here. I get the quad-copter (Maruader drone, whatever its called) on Liberty Island to about half health, and.... Delta'd. It's happened about 7x times now, plus another time with some other people. I left the group because real life happened, and they were able to continue and finish the mission. I've restarted my router, x-box, and even restarted the mission twice. No dice. Half health, then I get delta'd.

You could set your watch by it. Very glad I saw this post, because that means at least its not on my end. But the fact that its occurring with multiple gunships across different missions is still very upsetting.

Dev's, come on. You know whose frakking things up in your department, stop covering for them. Their making you all look incompetent. Time to throw them under the bus like the first wave.

Can also confirm. Marauder at Liberty Island mission is creating a Delta 3.

@cortez667 Hi I'm getting the same delta error on the kenner mission.

Hi would like to report that I'm getting a delta 03 error when I start fighting the marauder drone in the kenner mission.

I cant find any other posts in this mess of a forums about this but snap wife and I just tried this mission and get the same error at the marauder, I literally did it again last night on my alt as the daily or season - dont remember which tbh - so something has happened client side to affect this error

I'll add my +1 for the same "Delta-03" bug when fighting the Marauder on the Pentagon mission.

Heroic difficulty, no directives, build was turret/drone skills. The disconnect seemed somewhat connected to the health of the Marauder, it would disconnect constantly between the 25-50% range. Like someone else mentioned...you can reconnect immediately and it'll put you back at the last checkpoint for Pentagon mission and retain your place in the fight. I just threw the turret on the roof and it finished off the Marauder - but there was one more disconnect in that interim. Was able to complete the mission and there wasn't any further connection issues.

I had the same issue twice when fighting the marauder drones in West Potomac on challenging. The other person in my group also delta'd both times. We then went to play the Pentagon mission on challenging and both had deltas repeatedly on the first marauder drone fight. After three tries, the game ceased to be fun anymore, so we quit. It did seem to be related to the level of damage on the drone until the last two tries, which crashed almost immediately. Please fix this so we can finish the Pentagon mission for the weekly project. The weirdest part is that we both hadn't had a crash in a long, long time prior to tonight. Five crashes in less than a half hour, all when fighting a marauder drone, was new and unusual.

@jonnyybagg Same here. Started yesterday. Same error today.

@JonnyyBagg I just read on a different post and noticed myself, if you get kicked for Delta 3, log back in and your progress will be saved on destroying the marauder. I didn't go to the next area to fight it. I was respawned in the area where the razorback was and I fought it there. I was kicked about 5-8 times and logged back in each time, was respawned, and finally ended up destroying it. Good luck.

Got disconnected yesterday and tonight while playing Roosevelt Legendary, near the end of the mission when the 2 big drones (named marauder drones?) spawn. Both times everyone in my group got disconnected. Disconnect happened after my team jumped down from the wall.

This afternoon, on Dark Hours Raid Normal, Boomer phase.... all 8 of us got disconnected.

@SavageCarWash same here and for all players doing todays daily "pentagon" mission, delta crash after encounter the marauder drone at the end.
It's so sad to see. I quit playing for a while when the crash to desktop hit the PC players.

@bluemol Just tried to do the pentagon mission on story mode. There it saves the game when i get delta error. but it is an anoying almost no end of return point since you have to be fast to transport out to be able to continue to play the game elsewhere.

Hi All,
During the Liberty Island mission when you face the Marauder boss for the first time I keep disconnecting. Rest of the game seems to be running fine . I've tried running it 5 times so far and get the DC error every time.