Forge/Fabric: Forge
Observed Behavior: I stopped my server to add Curious Elytra after discovering that my newly crafted Silent Gear elytra could be equipped to a back slot. Upon starting my server again, I could not connect. My brother, who didn't have his elytra already equipped, was able to join. However, when he equipped his elytra, it crashed his client.
Expected Behavior: Happily flying away with my elytra.
Steps to Reproduce:
Use Silent Gear.
Craft an elytra using the SGear blueprint (I used only phantom membrane; idk if that is important).
Use the above versions of Curious Elytra, Curios, and Caelus, as well as Silent Gear 2.6.0+217.
Equip elytra in back slot.
(not sure if these steps will reproduce the problem exactly, but these are the only steps I did other than already having other mods installed, which you can see in the crash log).
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Versions:
Crash Log: https://pastebin.com/4SRyjuKQ