I have been playing in this world for some time already and just added the 1.20.1 builds of Spartan Weaponry and Shields (btw, big thanks for updating it, I missed it from 1.16.5).
When adding both mods, the world crashes and reports the following:
crash-2024-06-14_11.08.30-client.txt
It happened twice, and solved when removing the mods, so I'm sure it has to do with them. In case it's needed, here's also the latest.log.
latest.log
I hope it can be fixed soon, and again, thanks for updating your mods, they are awesome!

I'm not sure how to properly move it, but I found another bug report about the same thing and commented with this issue link. Thanks for ur help

crash-2024-06-15_15.28.25-server.txt
Same as me, I also experience this too.

Post it too on the Shields issue page, might be more useful there

This may only be related to spartan shields, since they use banners in their recipes. I assume you would be safe if you only use spartan weaponry with supplementaries.

You were right! Works fine with only Spartan Weaponry, thanks. (Tho shields still would need a fix)

You should move this issue to the spartan shield repo

Thanks for the reports,
I'm gonna close this issue since it isn't related to Spartan Weaponry. Keep an update on it here: ObliviousSpartan/SpartanShields#3