I have the latest terrestria mod version in my server. Everytime any of the players is trying to use any of the boat entities from Terrestria the Chunk gets bugged and the player lost connection from the server and it is unable to connect again. Any other players that get into the chunk where the error happened also get disconnected and bugged. The first time was using a terrestria:cypress_boat entity .
Afterwards I tested if the same issue happened on single player but all worked fine and I wasn't able to reproduce the error.
I rolled back the server to the previous back up version and did some tests. Spawning the boat is okay, use it causes the crash. It doesn't only happen with the cypress boat but with all the other boats belonging to Terrestia.
Crash doesn't happen when original minecraft boat entities are used.

Should you need more information please let me know it.

crash_report21.06.2023.log

Could you post the client log as well? The server log and disconnect screen doesn't provide enough information to debug a networking issue.

Hey thanks for the answer, I will upload few of my logs with some comments. I was testing most of the afternoon.
The only thing that could fix the issue was to complete rollback the server to before my user try to use the cypress boat.
2023-06-21-2.log
2023-06-21-5.log
User_Le_Evee.log

a video I took with my phone yesterday doing a test https://drive.google.com/file/d/1WX-kdTEYdddmwKfHyHHIC6ZYRevNY8_m/view?usp=sharing

I'm out of time for the moment but three things in case Haykam takes a look in the meantime:

First, you are using a mighty old version of Terrestria (6.0.0 vs. 6.0.7 which is the actual latest). I tried reverting my test environment to 6.0.0 and it did not crash so that is not the problem per se. However, many bugs have been fixed since 6.0.0.

Second, you are using Sodium and Iris with a bunch of other mods; it is strongly advised to also install Indium in this situation unless you somehow know none of your other mods are using FREX. I suggest adding Indium and testing to make sure that doesn't resolve the problem. However, the lack of stack trace does make this iffy at best.
https://modrinth.com/mod/indium

Finally, testing in general with both Fabric and Quilt and after adding in Sodium and Iris does not reproduce the problem. It is likely necessary to test the entire modpack to reproduce (if we don't get unlucky and still fail to reproduce even at that point). Is this modpack available on CF or Modrinth?

will try to add lithium

Indium :) but yeah I don't have great confidence in this, it'd just be nice to eliminate it.

Heyho, yeah Indium sowy! I updated all the possible mods for the version we used and add Indium. Did again another test and again game crushes.
I attach server log and my client log.
server_log_22.06.23.txt
suzzlein23.06.23.log

I have re-created this set of mods as faithfully as I am able, with the exception of the mod njb 1.0.1 which does not exist on either CF or Modrinth. However, although this combination of mods crashes frequently due to invalid structure generation and server-side OOM events, I cannot reproduce the Terrestria-related failure. It is therefore my opinion it is not terribly likely Terrestria is at fault for the crashes in question, even though they seem proximate.

In order for us (or me at least) to further pursue this issue, I want to see it reproduced without a bunch of other unstable mods.

@Suzzlein @gniftygnome My server has the same problem, boats and all. It's not a fluke, but it seems we don't know the missing factor that's causing it for some people and not others. Right now i'm going to test removing non-content mods from the server, and if that doesn't work, we're going to have to ban the boat items and delete their entities.

My server has the same problem

We really need to be able to reproduce this and so far we can't. The OP had at least one mod that wasn't available to us. We need your logs, or at the very least, a comprehensive list of your launcher version, loader version, and every installed mod and its version (this is all in the logs though).

For bonus points if you're willing and able, a copy of the world, or at least the region data containing the bugged chunk might also be useful.