Description of the issue:

I'm encountering several stability issues with skyhooks on a multiplayer server.

Was trying to use skyhook on an insulated LV wire between two powered lanterns on top of wooden posts (the IE treated wood ones) when I got my player into a bad state. Server disconnects me with "Invalid move player packet received" whenever I try to log into the server.

It took me a couple tries to get on the line and I was able to briefly attach successfully. It might be that attaching close to one of the lanterns triggered the disconnect/invalid position.

Update - edited my player to get Y coordinate back into the world and was able to play around some more. One misunderstanding I had was that you have to hold down RMB to use the skyhook properly. I was clicking and releasing quickly when I encountered the issue.

Crashlog:

First disconnect (note that there are no messages between crafting the skyhook and then actually trying to use it 30 minutes later):

Mar 12 23:31:43 mc-server supervisord: mc-server [23:31:43] [Server thread/INFO]: sollaires has made the advancement [Booker, catch!]
Mar 13 00:05:06 mc-server supervisord: mc-server [00:05:06] [Server thread/INFO]: sollaires lost connection: Invalid move player packet received
Mar 13 00:05:06 mc-server supervisord: mc-server [00:05:06] [Server thread/INFO]: sollaires left the game

Server logs on connection (Maybe note the NaN in the player position?)

Mar 13 00:27:51 mc-server supervisord: mc-server [00:27:51] [Server thread/INFO]: sollaires[/X.X.X.X:58752] logged in with entity id 420 at (-81.94579111426903, NaN, 646.5)
Mar 13 00:27:51 mc-server supervisord: mc-server [00:27:51] [Server thread/INFO]: sollaires joined the game
Mar 13 00:27:51 mc-server supervisord: mc-server [00:27:51] [Server thread/INFO] [journeymap]: sollaires joining dimension 0
Mar 13 00:27:51 mc-server supervisord: mc-server [00:27:51] [Server thread/INFO] [journeymap]: Sending log in packet.
Mar 13 00:27:53 mc-server supervisord: mc-server [00:27:53] [Server thread/INFO]: sollaires lost connection: Invalid move player packet received
Mar 13 00:27:53 mc-server supervisord: mc-server [00:27:53] [Server thread/INFO]: sollaires left the game

Some stack trace logs from the server when just playing around with the skyhook resulting in a different permanent disconnect loop:

https://pastebin.com/X31Xm4Kj

Versions & Modlist

Same mod versions from my other recently created issue: https://pastebin.com/zv75DEnM (this is not a crash log for this issue)

One note that might be useful in a README or somewhere is that allow-flight=true is probably desired for an IE server. I haven't been able to repro the invalid position again but I was able to get the server to kick me for not allowing flying.

Playing around some more and I've gotten myself into a pickle I can't solve. Getting disconnected every time I try to connect with this showing up in the server logs:

https://pastebin.com/X31Xm4Kj

Edited Pos in my player .dat file but I'm still crashing on login. Any other data on my player I can edit to get out of the attached mode or maybe solve the disconnect loop?

One last note for now - deleting the RootVehicle entry in my .dat file let me log back in.

10 minutes of RMB spamming yielded no NaNs. However, the game jerks the play around a lot when the hook gets in range of a wire. I also unlocked boat recipes when I stepped into water after succesful sky-hooking.

I looked at https://pastebin.com/X31Xm4Kj
The NPE at MessageSkyhookSync.java:63 is likely a side-effect of losing the connection (connection.writeToNBT())
The NPE at EntitySkylineHook.java:103 possibly also the same ((this.ticksExisted==1&&!world.isRemote))
They repeat 16 times each and there is nothing more there.

I experienced something simmilar, trying to use the skyhook on a rope between two structural connectors. The client as well as the server crashed and had to be killed.
It might have something to do, with the rope theoretically pulling the player through a block ... (at least in my case, the rope has a rather extreme slope, which gets it just above the edge of the block)

This is probably fixed in the next IE build (81), see #2937. I'm going to close this, please put a comment here if this happens again with IE 81 or maven build 363+. The existing broken players need to be fixed manually as I said in the other issue.