In fact it does not seem to only be when loading a savegame.
We have tried quite a few custom maps now and some of them mark all objectives as completed when we start the game. Even when looking at the map and waiting for the other player it shows completed as soon as my friend is ready.

danczer is correct.
Did some more tests and the objectives are only marked as failed when the second player joins.

http://feedback.arma3.com/view.php?id=6178 //When resuming a savegame close to enemy in coop the player will run around, engage and get killed while savegame still loading

http://feedback.arma3.com/view.php?id=17305 //Loading savegame incorrectly marks all tasks as completed/failed on custom multiplayer coop maps

http://feedback.arma3.com/view.php?id=17320 //Regular desysnc when playing coop on maps

Third party script

I apologize was not aware that this is a third party script.

Glad it is fixed! Very anoying.

I know I have seen it work but also lots of occasions where it does not and should have killed the enemy.
Maybe it is an armor issue - absorbing too much damage?

I dont know about the actual mechanics of the health system but from experience in normal combat situations the enemy almost never dies from a close grenade explosion.

The standard frag grenade

This is extremely frustrating! Last night again after me and my friend had to stop our campaign after both dying we had to click on suspend because there is not quit to main menu option. Which meant that our user save becomes useless due to the game always choosing the latest save when resuming. This effectively broke our game because it is loading the suspend (continue.save) where we are both dead. :-(

Only way to get past this is to delete the continue save file in which case the game word normally load the user save but this is not a solution.

This could be easily resolved by allowing the user to choose which savegame file to load when resuming a coop campaign and ties into tracker number 0006186.

Have not seen this issue again so far.

This seems to happen if all the players die within the respawn period and the mission then aborts without saving, leaving the continue savegame older than the last user savegame.

This happened in escape from Stratis coop scenario

Have not seen this issue again so far.

Thanks I will keep an eye out for this issue

I also think the rearm icon must then be the default shown if the dead soldier or container has ammo compatible with the players gun otherwise it must show the weapon swap icon.

Yes I have tested again and agree with you. The confusion came in with the icons and the exchange weapon icon being the default.
Please change as per your suggestion.

This is extremely frustrating! Last night again after me and my friend had to stop our campaign after both dying we had to click on suspend because there is no quit to main menu option. Which meant that our earlier user save becomes useless due to the game always choosing the latest save when resuming. This effectively broke our game because it is loading the suspend (continue.save) where we are both dead. :-(

Only way to get past this is to delete the continue save file in which case the game word normally load the user save but this is not a solution.

I agree there should be an abort option. If you die and want to "abort" it saves which means you cannot continue the game because the continue save file is the one that will be used and now one or more players are dead. Then you have to go and delete the continue savegame file in order for the resume to load the latest user save instead.