[1.21.1] Invisible player body in Flashback replays. Possible coremod conflict between mixins and NeoForge's base coremod system.

[VOLKOUL]

Minecraft version

1.21.1

Describe the bug

To start off, the second part of the title of this issue is a response I got from the developer of one of the mods this issue affects. The Flashback mod runs fine on Connector, but once certain mods are introduced, the player's body in any replay just ceases to exist, leaving only a flying head. This does not occur on Fabric (tested with the Fabric versions of the mods). The mods causing this (that I have found thus far) are Xaero's Worldmap and Nostalgic Tweaks.

Steps to reproduce

Easiest way:

1. Install Connector, Connector Extras, FFAPI, Flashback and Xaero's Worldmap
2. Record a replay
3. Enter the replay and get spooked

Additional context

The current officially available version of NostalgicTweaks needs to be edited to launch on 1.21.1 and causes lighting issues with Flashback, but there is a GitHub fork that fixes this, the link to which can be found in the NT's Discord. (since the developer of NT is on a hiatus others started to fix some bugs)

Also I know that this is technically a mod incompatibility issue, but from what I understand the "origin" of the issue is Connector sooo ¯_(ツ)_/¯

[Spud-Developer]

I found that when the player's body is invisible, if you go into spectator mode then back out, then the body reappears??
I think it might have something to do with spectator mode because of this
maybe it doesn't render the body because some problem with neoforge and spectator mode?
no clue.
but strange none the less :P

[VOLKOUL]

Your method doesn't seem to work for me, unfortunately. You might be referring to Flashback's "fake" camera-client body that appears when you switch gamemodes in a replay and which has one of Minecraft's default skins. It's not the same as the actual player in the recording.

Also, Flashback versions past 0.13.0 crash the game when trying to enter or create a world. Flashback 0.16.0 for 1.21.1 can be found in Flashback's Discord.

[VOLKOUL]

I am currently in the process of finding more mods in my modpack that cause this behavior. There are a lot of them. Some even make the entire player disappear, including the head. When this happens, the player seemingly ceases to exist altogether, as Flashback's "spectate player" selection menu is empty. It also spawns the camera in a different location.

[Spud-Developer]

Oh, well I wasn't talking about the "Replay Viewer" fake player when seeing a replay, For me I simply just ran '/gamemode survival @A' then set the replay viewer back to spectator and all bodies reappeared, though it goes back to being a head once they die or you go back in the replay, making it reload everything. The player ceasing to exist altogether could be from a mod changing how the game renders or the way the player renders, I'm not sure :3

…

On Tue, 4 Feb 2025, 3:41 am VOLKOUL, ***@***.***> wrote: I am currently in the process of finding more mods in my modpack that cause this behavior. *There are a lot of them.* Some even make the entire player disappear, including the head. When this happens, the player seemingly ceases to exist altogether, as Flashback's "spectate player" selection menu is empty. It also spawns the camera in a different location. — Reply to this email directly, view it on GitHub <#1452 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BKPEFWQYWRYY6FEU5C2QYMT2N6L3XAVCNFSM6AAAAABPOKLIFGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMMZRGUYTQMRSGY> . You are receiving this because you commented.Message ID: ***@***.***>

[VOLKOUL]

After what feels like eternity here are all the mods that I found which break Flashback: (there are a few mods included that are dependents of others)

Aether
Backpacked
Carryon
CMDcam
Comforts
Configured
Dummmmmmy
FastFurnace
FastWorkbench
ImmersiveEngineering
Jade
Kiwi
LittleTiles
Mekanism (+addons)
Moonlight
NostalgicTweaks
Placebo
Prone was pressed
SnowRealMagic
Supplementaries
Titanium
TwilightForest
Waystones
XaerosMinimap
XaerosWorldMap

Ur welcome :>

[VOLKOUL]

There are some unique cases like Carryon making the entire body (head included) disappear and Mekanism crashing the game when exiting replays. Most mods however only "delete" just the body.