Incompatibility with several different mods across both Fabric and NeoForge (Sinytra Connector)

[therealyocow]

Cross-posted from the Marium's Soulslike Weaponry Issues page with additional information, as I have found there to be more mods that don't play nice with Switchy specifically;

Minecraft: 1.21.1
Fabric: 0.19.3, also observable on NeoForge 21.1.238 via Sinytra Connector 2.0-beta 15
Switchy: 3.7.1

Affected mods (that I have noticed):
Soulslike-Weaponry 1.4.8
Fazcraft 5.4.3
Unusual End 2.3

Describe the bug
When switching profiles with one of the affected mods loaded, the client is immediately disconnected. On the server's end, an error relating to the handling of custom payloads is seen in the logs. The issue seems to differ between Fabric and NeoForge, but the cause and end result remain the same. Error does not present on Switchy versions before 3.0.0, so it appears to be an issue with the reconfigure/hotswap done on more recent versions

Add logs
NeoForge log (done in singleplayer, hence server logs and client logs are merged): https://mclo.gs/MXZE5T2
Fabric log (also done in singleplayer): https://mclo.gs/uoolRP8
Additional NeoForge log with other affected mods: https://mclo.gs/w3jE3cY

Steps to reproduce the behavior:

1. Create a fresh instance of Minecraft 1.21.1 with either Fabric or NeoForge
2. Install Switchy and any of the affected mods
3. Create a new world or join a server
4. Execute a Switchy command (e.g. /switchy and following the instructions, or using /switch <name> if a profile already exists)

Expected behavior
Player is expected to auto-reconnect with the new Switchy profile applied as normal