how do i fix this weird glitch on my aternos server

greetings,

recently some strange glitches have appeared on my modded server that affected everyone

i have checked and shaders does not create this issue

any help will be appreciated

Quote from Roman

Provide more information about your server.

Software, mods, plugins, settings etc.

software is forge, 1.16.5 (36.1.0)

there's 10 mods on the server, i'll list them below
SecurityCraft v1.8.21.1 (1.16.5)
MrCrayfish's Gun Mod v1.0.1 (1.16.3)
Create v0.3.1c (1.16.5)
Decorative Blocks v1.7.2 (1.16.4)
Eternal Winter v1.3 (1.16.5)
Kiwi v3.5.1 (1.16.5)
Nef's Medieval decoration v0.8 (1.16.5)
obfuscate v0.6.0 (1.16.3)
Simple Planes v4.4.1 (1.16.5)
Snow! Real Magic v2.5.7 (1.16.4)

for the settings we've got:
Slots: 20
Difficulty: Normal
Cracked: On
Commandblocks: On
Animals: On
Villagers: On
Force Gamemode: Off
Gamemode: Survival
PVP: On
Fly: On
Monster: On
Nether: On
Spawn Protection: 0
there's no plugins

Quote from Roman

Try removing mod by mod

Create a backup before.

alright thanks, i will try

Quote from Roman

Try removing mod by mod

Create a backup before.

i have tried right now and it did not work