Modpack version
0.5.9

1. I died and picked up my gravestone at the same time. Then I went back to the gravestone I just created and picked it up, the items in the inventory and armor slots which should be stored in the gravestone disappeared. Only the baubles (ex: backpack, necklace etc.) remained.
2. The "step assist" function in the hydraulic propulsion unit doesn't work. I am sure I have enabled it.

The second issue is a duplicate of #2472 and should be fixed in the next release.

The mod author asked for your latest.log :) If you were playing on a server, could you please provide the server's latest log as well?

Thanks for the report, I relayed it.

I was single player, but I still upload the logs.
https://drive.google.com/file/d/1yDjaDqKCOgxwAKaRWJgSetbFKqzuzhuC/view?usp=sharing

Thanks! Did you try to restore the grave through commands?

None of those logs contain any deaths, do you have the latest.log from when this bug occurred?

Sorry, I don't know which command I should use to restore the grave. On the other hand, I updated the version recently, so I think I got the versions mixed up. It should be Enigmatica6-0.5.8.
It is the log. https://drive.google.com/file/d/1JsDjmXrEu1jls-ypYeZlV2bsi5y_-KCT/view?usp=sharing
The incident happened after 2021-8-10. (Sorry, I don't remember the exact date)

Google Docs

logs (1).zip

I'm sorry but I don't have time to pour through that many logs :/ if it happens again feel free to comment here, but for the time being I'm gonna close this, it's extremely edge case anyway.

You can restore commands through /graves playername restore death_number

I've had this happen as a player on a multiplayer server running version 0.5.21 of the modpack.

I got one-shotted by a boss from a spawner (a Wraith that spawned with a weapon and a damage buff), then died again between clicking on my grave and getting my items. When I did reclaim my grave a second time, all I got back were my curios/baubles; everything else was just gone.

Since I am a player, not a server admin, I can't provide logs. This doesn't really help much, which is unfortunate. I suppose the gravestone mod trips on itself if you die while the game is processing returning your items from the grave marker. The only thing that can help pin this down more precisely is if someone provides definitive logs that can show this bug in action as it happens.

In the meantime, is it possible to give the recently killed player a grace period of damage immunity (or have the mobs ignore them) so they can get to their graves and claim them? Needs to be a short one, like 2 minutes, and this grace period should end once the grave is claimed.

Oh yeah, the grave finder you get on death persists in your inventory after reclaiming your stuff when this bug rears its head. Just thought I'd toss that in too. You reclaim your bugged gravestone, the grave finder remains in your inventory like a reminder that something went wrong.

You always keep the grave finder.