I don't know how to replicate this, but every single person on my server now sees banners mirrored like in the top right corner. I've tried messing with the settings in case it had something to do with that, but i wasn't able to fix anything. Im in fabric 1.20.1 version 0.16.7

This is my mod list:
Create Slice & Dice (by possible_triangle)
Create: Numismatics (by IThundxr)
Fabric Language Kotlin (by modmuss50)
Macaw's Paths and Pavings (by sketch_macaw)
Additional Banners (by DarkhaxDev)
Farmer's Delight Refabricated (by MerchantPug)
Chisel Reborn [Forge/Fabric/NeoForge] (by Slaincow)
Macaw's Trapdoors (by sketch_macaw)
Indium (by comp500)
ModernFix (by embeddedt)
Tectonic (by Apollo)
SuperMartijn642's Core Lib (by SuperMartijn642)
Lithium (Fabric/NeoForge) (by JellySquid)
AppleSkin (by squeek502)
Automobility (by FoundationGames)
Modern KeyBinding [Fabric] (by MikhailTapio)
Create Deco Fabric (by talrey)
Tom's Simple Storage Mod (Fabric) (by tom54541)
Eureka! Ships! for Valkyrien Skies (Forge/Fabric) (by rubydesic)
Amendments (by plantspookable)
Simple Voice Chat (by henkelmax)
Macaw's Doors (by sketch_macaw)
Origins (Fabric) (by Apace)
IngotCraft (by jahirtrap)
Daily Rewards (by Kaworru)
Create: Bells & Whistles (by syslev)
Create: Ultimate Factory [Forge/Fabric] (by robinfrt)
Dig's DnD Origins (by distantdig)
Create Big Cannons (by rbasamoyai)
Sophisticated Core (Unofficial Fabric port) (by salandora)
Sodium (by JellySquid)
Small Ships [Fabric & Forge] (by talhanation)
Create Fabric (by tropheusj)
NetherPortalFix (Fabric Edition) (by BlayTheNinth)
Jade 🔍 (by Snownee)
Macaw's Furniture (by sketch_macaw)
Clockwork: Create x Valkyrien Skies (by rubydesic)
Macaw's Holidays (by sketch_macaw)
Sophisticated Backpacks (Unofficial Fabric port) (by salandora)
Comforts (Fabric/Forge/Quilt) (by TheIllusiveC4)
Balm (Fabric Edition) (by BlayTheNinth)
Cosmetic Armor [FABRIC] (by Apace)
Handcrafted (by terrariumearth)
Create: Diesel Generators [Fabric] (by MrSterner_)
Fabric API (by modmuss50)
Clumps (by Jaredlll08)
Athena (by CodexAdrian)
Macaw's Fences and Walls (by sketch_macaw)
Create: Steam 'n' Rails (by IThundxr)
Mod Menu (by Prospector)
Bookshelf (by DarkhaxDev)
SuperMartijn642's Config Lib (by SuperMartijn642)
Macaw's Paintings (by sketch_macaw)
Supplementaries (by MehVahdJukaar)
Chunk Loaders (by SuperMartijn642)
Create: Let The Adventure Begin (by Not_Juno)
Skin Restorer (by Lionarius)
GeckoLib (by Gecko)
Cloth Config API (Fabric/Forge/NeoForge) (by shedaniel)
Trade Cycling (by henkelmax)
Effortless Building (Fabric) (by falincult)
Macaw's Lights and Lamps (by sketch_macaw)
Reimagined (by Reijvi)
Pehkui (by Virtuoel)
Valkyrien Skies (Forge/Fabric) (by triode_)
Vertical Slabs Compat (by MehVahdJukaar)
Resourceful Lib (by ThatGravyBoat)
Eureka! Create Airships! (by End_Rage)
JourneyMap (by techbrew)
Architectury API (Fabric/Forge/NeoForge) (by shedaniel)
Moonlight Lib (by MehVahdJukaar)
Iris Shaders (by coderbot)
Alternative Rain Sounds (by paoleks)
Just Enough Items (JEI) (by mezz)
Macaw's Bridges (by sketch_macaw)
MapFrontiers (by meme_sapiens)
Complementary Shaders - Unbound (by EminGT)
Trinkets (Fabric) (by EmilyPloszaj)
Forge Config API Port (by Fuzs)
Mouse Tweaks (by YaLTeR)

It's probably an incompatibility with some other mod. I don't do updates for 1.20.1 anymore unless it's something really serious. Sorry.

If you are still using 1.20.1 and MapFrontiers, could you please try the new version 2.6.0p6 and tell me if it fixes your problem?

Yes, now it works fine, thanks!

Perfect. Thank you.